not completely true, you can get aways without using a primer, the original paint from Honda on that piece is a urethane based paint, you can get away with not using a primer if you scuff the paint thats on there, the paint its self needs a tooth to bite into, paint bonds in two ways theres a chemical bond and a mechanical bond, if you scuff the paint(creating a mechanical bond), using something like a 3m grey scuff pads from any auto parts store you can apply color directly to that, after making sure its super clean tho, when you scuff it you need to essentially take the shine off of it it should look dull and flat when you're done.

the Italian red comes in numerous factory variance colors, the one they list for the 98 has a base coat and a mid coat, also know as a 3 stage color (base, mid , clear), you will need both of them to make a perfect match, if you want to save some money you can buy the Italian red for a 04 VFR it comes as just a base, just put down a couple coats of red and clear it, no need for the 2 different paints, the color of the VFR is slightly lighter but you would never notice with the belly pan being so far away, if you painted the side faring and attached it to the nose piece you would panel to panel like that you would see a difference

hopefully this helped a little