Base paint was a white/grey, painted on top of that a khaki that turned yellow/med. To mustard. I painted white primer on it and then proceeded to paint the color I found which is a tan with no yellow. I tested a spot and was shocked to see it change very dark and extremely brownish/yellow. Do I need to let it dry completely and then try to paint another coat of the preferred color over it?

U said "paint found''. Is this a color off the shelf at store or did u ''find it'' in your basement/garage?

Test paint on area where u tested before and see if u get the color u want. Most paints take two coats to cover without bleeding.If at all possible, in future, tint primer to match color of finish.

Chuck