The best paint conversion charts I have found are located here: https://redgrimm.github.io/paint-conversion/index.html
Example showing in the screen shot below using the example Yriel Yellow by Citidel:
- An equivalent or similar paint in another brand (in this case Vallejo)
- The original colour
- The mathematical difference between these 2 colours
Thanks to whoever put them up there they are great!, i hope they never disappear!