Pick good blocks for pixel art?

MitBoy

Terrarian
So, there's some kind of color sheet, but doesn't really help. First I wanted to download omnitool (just to see which blocks it will use), but convert image into map doesn't work for some reason. So is there some kind of online thing or tool to do that? Paints probably won't work, since there's no specific colors.
Here's the pic, btw.
adagiodazzle.png
 
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