The Color type represents a color as float red, green, blue, and alpha "components". The color components (red, green, and blue) represent the actual "color", while the alpha component represents the opacity when a color is blended onto a background.
Component values are commonly in the range 0.0 to 1.0, for example "white" has red, green, blue values all equal to 1, while "black" has them all equal to 0. Color values outside this range cannot be directly displayed on standard computer monitors, however they may still be useful for mathematical operations and rendering. For example, color values "above 1" will cause bloom when rendered.
The ColorX type stores a Color along with color space information, and is therefore more commonly used.