Here's the problem: I'm trying to paint over a bright green/teal color
that hasn't been updated since the 50s, and it's on plaster walls. In
one room I've put on 2 coats of off-white, Classic 99 Sherwin Williams
paint; no primer. In that room the white has covered most of it, but
there is a blueish color leaking through.

In another room I put 1 coat of Sherwin Williams Superpaint in a
vibrant red color over the same green/teal, and this time a different
problem has come up. The coverage was much better on account of the
bright red color, but there are parts of the red walls that came up a
little lighter and splotchy when it all dried. Will another coat fix
this or will the same problems arise?

I've worked for a pro painter for a few years and he has never used
primer. On all my other jobs I've had beautiful results without
primer. However, on this job, I fear that the lack of primer may be my
downfall. I'm using high quality paint and my application methods are
not the issue.

Should I try to cover the green/teal with primer before painting any
more, or does anyone see another issue here that I'm overlooking?

Thanks for any advice!