Grainy Gradients cannot be more popular. Here is how to make this look with effects completely in after effects. This is one of many methods for making this look. We might use layer styles. We might use blending modes. BUT this uses effects and it's pretty dang good. Go here to watch it: https://youtu.be/0M9qe8_LhLo
This project file is intended for educational purposes only. It works in Adobe After Effects cs5.5 and newer.