I found a good resource for my kids, where I can buy or get some of the materials for free on this website and I want to share it with you
https://www.teacherspayteachers.com/Product/APPLE-Pop-Art-Interactive-Coloring-Sheet-1344191
This pop art coloring picture is made by Jenny K.
It is supposed to be for kids but I enjoyed coloring it myself too. I like how colors are contrasting making the whole picture bright.
I used soft coloring pensils.