Painting the inside is the best idea, but make sure you do a generous clear coat and allow it to try completely or you will have serious issues.
Also, depending on how much paint you use it could make the loader noticeably heavier.
Originally Posted by Staninator
I would recommend lightly sanding the inside so that the paint will stick and talk to your local dhardware store about priming it with something that works well for plastic so that it wouldn't start to chip away after regular use. Good Luck!
As long as you sand (just a little bit) and use Krylon Fusion or any other type of paint designed for plastics you should be fine.