Hello there!
I'm struggling with a simple thing. See what I got:
I dithered the balloon, what's not correct. But every version without dithering looked weird, and I don't want to use to many colours. In the version on the left, I handcrafted my own colour ramp. The dithering can't be seen here, because the colours are hardly different.
For the right version I used the colours of this picture:
http://orig03.deviantart.net/819f/f/2015/270/5/b/day_66___365___balloon_by_deneesi-d9b3qwt.png I liked how the colours worked "as a balloon", but they doesn't seem to fit with my sprite. Here the dithering is going on a rampage.
The highlight brings me trouble as well, as the straight top line does.
I think the problems can be fixed with better colours. But the less saturated didn't look realistic, as balloons are "covered" with light caused by the flat surface.
Hope you have something in mind.