What colour primer should I use when painting red?

The main thing to remember about primers is that the brighter the primer, the brighter the topcoat.

So if you want your model to really stand out when using bright colours, use a white primer.

For example, if you were to paint a post box red, if you prime it with a white primer the red will look bright and vibrant.

If you were to prime the post box with a black primer and then paint the post box red it will still be red, but it will appear a lot darker and duller.

If you are still unsure have a practice on a piece of sprue with both primer colours and then decide which is the colour best suited for your needs.