Hellobee Boards

Create a new layer, place it on top of your project, and use the paint bucket to fill with a color similar to your paper. Then change the layer properties to reduce the opacity - maybe 30-50%, not sure how saturated your paper is.

If you put it under it won't have any effect on your other layers (since they're opaque) although you could see if you can get a sense by dropping the opacity of all of them to 80% or so.

ETA: It's hard to get true blues and greens on reds - good luck!

I agree with @Mrs.Someone: changing the layer's blend mode to multiply against the layer of the color of the paper would work best. I still would printout swatches of the color I would want to reproduce because the monitor color will always look different than the printer output.

@regberadaisy: You will want to use the lightest shade as your background color. So that the darker colors will pop out easily. It's hard for me to say which color that would be as there can be variation within a color. Meaning, not sure if the color of mint green for example, is a light shade versus a saturated shade. Just my thoughts.