To earn the "Casual Puzzler" trophy in Pic-a-Pix Color, you must simply complete any 10x10 grid puzzle (Puzzles 6-50).
If you're struggling or want to work through this list quickly, you can just follow any of the 10x10 solutions in the below Google Drive folder I'm putting together. This will eventually contain every puzzle solution.
https://drive.google.com/open?id=1GouHjmn9DNF034KII1A96lGLKD...