Simply, do not believe what you see.
That was very frustrating for me, as well as for my art students. I started with watercolors personally, and was very used to seeing the color and they looked the same on paper.
Acrylics are different.
This is why it is recommend to put a swatch of color mix on a piece of paper and letting it dry.
Then, see if it is the correct color. Only after you are satisfied, apply it to the final piece/paper.