Graphics functions

`BLUE`	Calculates the blue components of RGB colour values.
`GRAY` or `GREY`	Calculates RGB colour values for values on the gray (grey) scale.
`GREEN`	Calculates the green components of RGB colour values.
`RED`	Calculates the red components of RGB colour values.
`RGB`	Calculates RGB colour values from red, green and blue components.

Updated on May 20, 2019