Mis-Tints
The Home Depot’s paint departments custom-tint thousands of gallons of paint each week. Given that volume, it’s no surprise that some of it doesn’t come out perfect, or is never picked up by the customer who requested it. Look for a shelf of “mis-tint” or “oops paint” for paint that’s priced so low it’s almost free.
Much like the wood found among the cull lumber, you may not find the color or quantity you’d like, but there’s often enough paint at a great price for painting doors or other small projects.