repainting hulls on a cat can you do a nice job DIY or hire a pro I want to change from white to red

if you have prep and paint skills and equipment and a wind proof location (with the correct filters for many modern paints) ... it is very possible
otherwise your results may not be so great

i have hulls that were painted grey (professionally)
looks great but ....

every scratch shows the white under it - extra noticeable

my grey hulls can get very hot in the sun 20% hotter than a white boat

I was hoping to give it a good sanding then either primer and marine paint of some sort or awlgrip is a paint I have heard for a durable nice finish I have a nacra 5.2 in nice condition and just wanted to make it look sharp and we all know red goes faster !!!

i have awgrip on my spars and imron over all fiberglass
it is a ridiculous amount of time and energy (and money) to get professional results
but doable if you have the time energy skills location and equipment (and money)

also 2 part pain is crazy toxin to human and environment so proper gear (full protection and enclosed paint both with filtration) is really important

depending on your current boat's condition - you may be better off with a thorough cleaning and polishing. gelcoat can clean up pretty well