Custom Paint - Workshop specials.

I imagine given that I'm 12 days late that you might already have progressed with this BUT...

Chromacoats need black beneath them to make the colour work "properly".

You can alter the groundcoat to alter the top colour effect... if your chromacoat shifts from blue to green to gold and you paint it over a green, it will instead have the effect of shifting more dramatically from blue to gold...

In terms of painting directly over a black primer, you can most certainly do this if you wish but in skipping the black groundcoat stage you're removing the opportunity for mid-process repairs.

Good practice would see you prime the bike, then put a key in the primer, then "spot prime" over place where you've accidentally burned through, then give a full even black groundcoat, and flip paint on top. If you have any inclusions in the finish when you're applying the flip, you can scuff it back a little and be safe in the knowledge that there's black beneath, then dust a little more in it's place... if you skip black and have an inclusion issue and you need to abrade paint away, you may end up exposing the substrate and need to start again.

The key you put in the primer will give you optimal bond between layers for a stronger, longer lasting finish. Importantly though, too coarse a key will show prep scratches in the flip paint (and silver and any product heavy with pearl or flake, and light in hue). The black intermediate groundcoat layer will minimise this effect by flooding prep scratches before the flip goes on.

For the BEST results with a flip paint, you would use this layering...
Wet on wet... primer, black, clear
Flatten, then flip, then clear, then flatten, clear.

You can also of course skip the black stage completely if you're working on carbon... just use a direct adhesion clear instead of a primer, then put the flip on.

Broadly speaking, you should always follow the instructions to the letter until you've mastered the products and tooling... if for no other reason than to understand how it's supposed to work according to the manufacturer and in trouble shooting, you'll potentially find solutions quicker.

Remember that when using rattle cans, you've already lost any control over the product blend or recipe, the product viscosity, the fan pattern, the pressure too... and some of these elements will change mid-process as the can loses pressure and you empty out the solvents and the pigment unevenly... changing more elements just makes the task a little trickier.