In every film, no matter the budget, there are a few roles that I think are essential and therefore you should make sure you have the best – even if it means paying for it.
First is DP (DOP, cinematographer), second is the location sound man/crew and third is the colorist. You want a pro looking film? Get a colorist. It’s that basic.
On vimeo is a great promo showing you just what a colorist can accomplish.
(note: if you want to see this in HD you have to go over to Vimeo. Click HD and follow the buttons).