Images:
https://www.freepik.com/free-photo/painted-relief-texture_1037471.htm#query=watercolor%20paper&position=9&from_view=keyword&track=ais

Shaders:
Watercolor: https://c-chen99.github.io/watercolorShader/final.html
CMKY: https://www.shadertoy.com/view/MltBW4
Fresnel: https://godotshaders.com/snippet/fresnel/