Does primer make paint darker?
Furthermore, does primer affect color?
primer has no effect on paint color at all as long as you get proper coverage. all it may effect is the amount of coats it takes to achieve proper coverage. In my experience yellow takes a little more to get full coverage than say, a red, so if your painter wants to use yellow sealer, great.
Also question is, does paint primer cover dark colors?
Covering a dark colored wall with a light color without first applying primer requires numerous coats of paint. By applying just two coats of primer, however, you can cover a dark color with even white or very light paint using only a couple of coats of paint.
Use multiple coats of primer Usually, you can get away with one coat of primer. But when it comes to painting over a dark color with a lighter one, two coats of primer(literally) put an extra layer between the colors and reduce the chances that the dark color will bleed through.