Color
There is color system
It refers to all the colors in the visible spectrum, with red, orange, yellow, green, blue, violet and other basic colors as the mixture, as well as the mixing of different amounts between and no color, and the thousands of colors produced belong to the color system. The greater the frequency, the greater the hue difference, and the larger the amplitude, the more obvious the difference between light and dark.
Any color in the color family has three major attributes, namely hue, lightness, and purity. That is to say, as long as the color has the above three attributes, it belongs to the color system.
There is no color system
A range of black, white and black and white shades of grey. Physically, they are not covered by the visible spectrum and therefore cannot be called colors. But visually, physiologically and psychologically, they have complete chromaticity and should be included in the color system.
According to a certain law of change, the colorless system gradually changes from white to light gray, medium gray, dark gray and finally black, which is called black and white series in color. The change from white to black in the black and white series can be represented by a vertical axis, with white at one end and black at the other, with various transitions of gray in between. Pure white is the ideal fully reflective object, and pure black is the ideal fully absorbing object. Therefore, there is no such thing as pure white and pure black in real life, it can only be infinitely close to pure black.
There are only colors without color.
Changes in brightness do not have the properties of hue and purity, that is, their hue and purity are theoretically equal to zero.
Three attributes of color
Hue
Hue is the appearance of the color after being perceived, or the name that distinguishes it from other colors, and the popular expression is the color name, when the name is the same, we use the surname to distinguish it. Such as red and magenta, red is the first name, and yang is the surname. Of course, red and magenta are both hues, and common hues such as red, orange, yellow, green, cyan, blue, and violet.
Hue is the main basis for distinguishing colors and is the biggest characteristic of colors. It is composed of primary, interchromatic, and polychromatic colors (see below for details).
Purity
Purity is the number of single standard color components contained in each color, and the popular expression is the degree of color brightness, fresh or not, also known as saturation. Pure color has a strong sense of color, and the chroma is strong, so purity is a sign of the strength of the color feeling.
Hue
Purity
Lightness. 
The purity that can be achieved by different hues is different, with red and blue having the highest purity, green having a lower purity, and the rest of the hues being in the middle and having different brightness. The fineness and smoothness of the surface structure of the object helps to improve the purity of the object's color.
Lightness.
Brightness is the difference between light and dark of color, or the difference between shades and shades, and the popular expression is whether the color is bright or not, dark or dark, and deep or deep. The lower the brightness, the closer it is to black, and the higher the brightness, the closer it is to white. We can understand it in layman's terms, how much white pigment is added to this color, and how much black pigment is added.
The upper part has increased the white gradient from left to right by 70% 0%.
There are two aspects to the difference in brightness of a color:
1.Variations in brightness of the same hue, such as pink, bright red, and deep red, are all red, but one is darker than the other.
2.There are differences in brightness between different hues, with white being the lightest, black being the deepest, and green and sky blue, red and royal blue being in a similar lightness.
Color relationships
Primary colors
The basic colors in a color that can no longer be broken down are called primary colors. There are three primary colors, namely red, yellow, and blue, which are units of color that can no longer be broken down.
1 primary color, 2 intermediate colors, 3 compound colors.
Intercolored
The color produced by the matching of every two groups of the three primary colors is called the intermediate color. There are only three colors of color and light: purple, yellow, and green (lake blue), such as red and green for yellow, green and blue for cyan, and blue and red for purple, also known as the second color.
Polycolor
The mixture of two intercolors or a primary color and its corresponding intercolor [red and green, yellow and violet, blue and orange] to obtain a compound color, also known as a tertiary color. The polychrome contains all the components of the primary color, but the proportions between the primary colors are not equal, resulting in a rich color gradient value.
Since the three primary colors are added to the white light, this has two consequences: one is that there is no compound color in the color light, and the other is that there is no gray color in the color light.
Homogeneous colors
The colors within the 15° angle in the hue ring are called homogeneous colors, and the hue properties of homogeneous colors are very similar, but the chroma is divided into shades. Such as dark red and light red, bright red and vermilion.
Neighbor colors
Colors within 60 degrees of the hue ring are neighboring colors. Between the neighboring colors, you often have me, and I have you. For example: vermilion and orange yellow, vermilion is mainly red, with a slight amount of yellow in it;Orange is predominantly yellow with a hint of red in it, and although they differ greatly in hue, they are visually relatively close.
Similar colors
The colors that are adjacent to each other within a 90-degree angle in the hue ring are collectively called similar colors. For example, red, red, orange, yellow, yellow, green, green, blue, purple, and so on are all similar colors. Similar colors are often used in color matching because the color ratio is not strong, giving people a sense of color, calm and harmony.
Contrasting colors
The two colors in the hue ring that are between 120 and 180 degrees apart are called contrasting colors. Also known as large-span color gamut contrast, it is a medium-strong contrast of hues, such as blue and red, orange and purple red, yellow-green and blue-violet are contrasting colors. At the same time, any color and black, white, gray, dark and light, cool and warm, light and dark are contrasting colors. A complementary color is a type of contrasting color.
Complementary colors
The two colors in the hue ring that are at a diameter (180 degrees diagonal) are called complementary colors. Red and green, orange and blue, yellow and purple are complementary colors. Put contrasting colors together. It will give people a strong sense of rejection. If mixed together, it will bring out a cloudy color.
In summary
Colors are divided into colorless and colored. Hue, purity, and brightness are the three major attributes of color, among which primary color, intermediate color, compound color, similar color, adjacent color, similar color, contrasting color, complementary color, etc. constitute the color relationship.
Understand the basics of color and the importance of relationships.
Cognitively: It is the interpretation of color and its attribute system, and is the basis for defining color sensory recognition;
Structurally: Defining the combination of colors is an important basis for intuitively judging the shape, structural texture and sense of space of the object
Application: The basis of color is color thinking, color association, color emotion, color contrast, color harmony...and other color applications of the stepping stone;
Familiar with the foundation and relationship of color, treat the world of color.