Using colors in excel and VBA is very simple.
The most used function is RGB(x, y, z). Where x is the variable for red color, y is for green and z is for blue.
All variables can have values from 0 to 255, where 0 is no color and 255 is the maximum level for that color.
Mixing those 3 variable you can obtain any composed color you need.
RGB(255,255,255) is white
RGB(255,0,0) is red
RGB(0,255,0) is green
RGB(0,0,255) is blue
RGB(0,0,0) is black
RGB(100,100,100) is grey
RGB(200,200,200) is light grey
RGB(255,255,0) is yellow