Two main methods for producing color in CRT Monitors are:
1. Beam Penetration Method
2. Shadow-Mask Method

Difference between Beam Penetration and Shadow Mask method.

Beam Penetration method Shadow Mask method
Where Used
 It is used with Random Scan System to display color. It is Used With Raster Scan System to display color.
Colors
 It can displays Only four colors i.e. Red , Green, Orange and Yellow. it can display Millions of colors.
Color Dependency
 Less colors are available because the colors in Beam Penetration depends on the speed of the electron beam. Millions of colors are available because the colors in Shadow Mask depends on the type of the ray.
Cost It is Less Expensive as compared to Shadow Mask. It is More Expensive than other methods.
Picture Quality Quality of  picture is not so good i.e. Poor with Beam Penetration Method. Shadow Mask gives realism in picture with shadow effect and millions of color.
Resolution It gives High Resolution. It gives Low Resolution.
Criteria In Beam Penetration method, Color display depends on how far electron excites outer Red layer and then Green layer. In Shadow Mask Method, there are no such criteria for producing colors. It is used in computers, in color TV etc.