Is white a color for screen printing for custom flags?

This question I don't really get asked its more people ask "I would like a custom flag made using my logo the colors in my logo are navy blue, red, yellow and white" After being a flag maker for many years I have found out that many flag manufacturers out there especially the one's on the internet say that the custom flag above is 4 colors when they quote you. This is not true!! The flag above is only 3 colors WHY? White is not a color So next time you go to have a custom flag made be shore they don't charge you for the color white. If you have white in your logo the flag makers will use white material, most flags are screen printed on white material anyway.