I use much color because I didn't palette before starting my creation. (Sorry if I have mistakes, I do not speak English very well)
That does seem an unnecessary amount of colors, but that's not something that bothers me overly. It's a nice piece, although the edges of the clouds don't look as smooth as they could.
I think I could do this with 10 colors, maybe less or a bit more. But 42? 121?
But, forgetting the colors, the piece is good, I think.
Sorry dude, but that png have 121 colours, not 42...
You should work this out, and also with only 21 colours you can get exactly the same results.
I think its the way you output / save your file that adds all the colors. png24 will add colors like that. png8 or gif will not.