here read this. You color sand after you spray the clear to smooth the finish and remove imperfections. Even with the best painter, perfect condition, and cleanest paint booth a typical paint job will have some texture (orange peel) and specs of dirt.
Once the clear coat drys for a few days (even sooner if it is baked) you wet sand the car with sand paper from the 800-2000 grit range, buff with an aggressive compound and pad, then polish with a super fine polish to remove micro scratches and swirls. This process is an absolute art (probably the most demanding of the paint process) and should be handled by a professional.
As far as sanding between the base coat and clear coat, it is not necessary with the modern paint systems. Now I might sand my final coat of base if there was an abnormal amount of dust or imperfections in the base, but I usually will apply one more coat of base coat before spraying the clear coat.
I use both Spies Hecker and Glasurit paint systems. I prefer the Spies Hecker, but some hard core Ferrari owner prefer that I use the Glasurit since it was the factory paint for so many years. I will usually spray 3-4 coats of base and 3-5 coats of clear (depending on how smooth I really plan on color sanding the car).
If it is a car that will needs to be "perfect" then this is my procedure.
3 coats of base
lightly sand the last coat of base with 800 grit paper to ensure smoothness
Spray a final coat of base
Wait 30 minuets
Spray 5 coats of Urethane Clear (I have a favorite that looks amazing) with 45 minuets in between coats (at 75 degrees)
Let air dry for 24 hours
Color sand with 800 grit on a rigid block
Let sit for 3-5 days so it can expel the solvent
color sand with 1000 grit with a rigid block
Color sand with 1500 with a soft pad
Color sand with a DA sander with 3000 trizat 3m paper
Buff with a 3m perfect-it wool pad and 3m perfect-it compound #1
Buff with a 3m perfect-it (white) foam pad and 3m perfect-it compound #1
Polish with a 3m perfect-it (grey) foam pad and 3m perfect-it microfinishing polish #2
Polish with a 3m perfect-it (blue) foam pad and 3m polish #3
Hand glaze with 3m hand glaze
If anyone wants the part numbers for these products let me know. I can tell you this procedure gives you an absolute show car finish. It is a lot of work, but well worth it!