Diamond faked dispersion (masked chromatic aberration ove single mesh of gem)

I have gold ring with diamond. I would like to fake dispertion on refracted mesh of gem by using chromatic aberration on it . I know there is something as stencil (mask for post production). I would like to use it aberration only on gem without gold ring mesh. Is it possible in unreal? Maybe some tips?

I would like to publish it as HTML5 but if it`s not possible I may test in on Windows.

I`ve read about stencils which are possible to use in HTML5 since 4.15. I know there are other methods but I thought that will be simple and usefull for faking dispersion.

Have you looked at this thread?