Apologies to Julie for taking this one on <g>... To keep it simple, try tis one.

IIf([Name]<>"xxx",switch([% Complete]=100,"blue",ProjDateDiff([Current Date],[Finish])/[Minutes Per Day]<=5,"red",ProjDateDiff([Current Date],[Finish])/[Minutes Per Day]<=10,"amber",ProjDateDiff([Current Date],[Finish])/[Minutes Per Day]>10,"green"),"")

It is the same as the original with a small section before AND after the previous formula, which should be easy to follow.