Red green gray color combination color values

Quick answer：

In design and color theory, red, green, and gray are commonly used to create various color palettes. Color values can be specified using different systems such as RGB (Red, Green, Blue), CMYK (Cyan, Magenta, Yellow, Key/Black), and HEX (Hexadecimal). For example, an RGB color value for red might be #FF0000, green could be #00FF00, and gray might range from #808080 to #FFFFFF depending on its lightness.