Welcome!
I'm also colour-coding parts on my car. You'll need
Abrasive paper - up to 2500 or 3000 grit
Alcohol wipes -- something suitable to clean and degrease the parts you're painting
Paint - you can get the colour code from the engine bay (on the driver's side firewall) and the paint you can get from most paint stores (including Halfords)
Primer - The paint you use may suggest a specific colour primer. My car is AJ4 (Flame Red), so Halfords suggested red primer.
Clear lacquer
Masking tape and sheet material to cover up parts you don't want to get blue on. Speaking from experience, get the low tack variety.
Optional but definitely worth it:
Automative polish - I used Auto Glym
Automotive wax - again, I used the Auto Glym variety.
If you can remove the part you're painting, do it. Makes life so much easier and you can keep them indoors whilst the paint dries.
First smooth out the plastics with the abrasive paper. The surface of the plastic will be rough, so work up the grades until it's nice and smooth. Leave some slight roughness to the surface so the primer has something to grab onto. If it's too smooth, then some 600 grit should help.
Clean the part with the alcohol wipe and allow to dry. If the parts are still on the car, then mask off the bits you don't want to be painting (wheels, lights, windows, seals etc). If you can remove the parts, then hang them off something using wire where possible.
Shake the hell out of the can, and if you can, try heating it up with a hair dryer to prevent the paint coming out too thick. Give the part a light dusting with the primer, using short bursts and a suitable distance to prevent runs. Leave a few minutes to dry, depending on the temperature. Once it's touch dry, you can apply another coat of primer. It's always better to to multiple thin coats then one or two thick coats which can result in paint runs (and more sanding later).
Once the primer is touch dry, you can repeat the procedure with the colour cans. The colour will need a fair few coats to get a good finish, and you will need to allow enough time for the paint to dry before moving onto the next coat. Patience is key here, as any corners cut here will definitely show up if you don't correct them later.
Once you have a few coats, leave the paint to cure (ideally for a few days if possible), then give the whole thing a wet sand with some fine abrasive paper (probably 1000 grit to start off with). You'll want a slightly dull finish. The purpose of this stage is to remove the orange peel effect you can get with rattle cans, you're not destroying your new paint (unless you use a coarse paper). Once you're done, clean the part again with alcohol wipes and crack open the lacquer.
This stage is pretty much the same as the colour stage, you'll need a few coats and a long cure time to ensure a tough finish. The lacquer will restore the shineyness you lost when sanding the colour. The more coats of lacquer you apply, the tougher the finish, but it will take much longer. Like the paint, short bursts and an even coverage. Once you've let this dry (preferably for a few days), wet sand it with 2500/3000 grit to remove any minor imperfections like orange peel. At this stage, a final coat of lacquer should finish this, but you can instead give the part a few passes with some resin polish and a few coats of wax to bring out a nice shine and protect it from the rain.
And I've been waffling on again. Sorry about that.
A bit of additional advice: some parts you can't remove for a long time because you'll need them to be able to drive your car (mirrors, tailgate plinth etc). Get down the scrap yard and grab some spares, then you can paint one set and then do the switch-a-roo in an afternoon, rather than rushing the job to get it done before night-time
Been hovering this forum for a while so thought I'd finally join
