I am painting a bedroom which I have undercoated with a white anti-mould paint. I have bought magnolia matt paint to paint over this but it shows up as a deep orangy/beige colour? However, if I put the magnolia paint on to say a piece of cardboard it comes up

I used a Behr primer in my new bathroom, only to find out that they suggest not painting over it. I used the 1-2-3 primer on all the walls. After painting the ceiling, I removed the tape and the paint peeled off as well. Any suggestions?