The darker the paint color, the more difficult it is to cover with a single coat. For some reason this is especially true for red paints. The general recommendation then is to tint your primer to give you a head start on the coverage. Since most primers start out being white there is only so much you can do to bring the primer color up to the finish color - you can only add just so much colorant to paint before it starts to perform poorly. Thus pink - or other pastel - primers.
I recently painted a bathroom a dark maroon, and even though I started out with tinted (pink) primer it took over five coats before I had complete coverage. I really didn’t notice any difference between painting over areas with the tinted primer vs. the non-tinted, but they insist that it matters, so what do I know.
**Napier **- It’s probably not the *color *of the patched areas but the *glossiness *of the paint that is showing through. My guess is that spackling will have the gloss equivalent to very flat paint, so if the rest of the wall is painted in satin or semi-gloss, you might see the patched areas jump out.