[HELP] what's the two color tweak using for?

[Selur]

For start use "Avisynth" or "Filtering" or "Vapoursynth" only mix these if you know what you are doing and you clearly do not and if you do there usually is no point in doing so.
Personally I would recommend to either use filters under "Filtering->Avisynth->Color" or "Filtering->Vapoursynth->Color" if those are available on your system, if those are not available use the filters under "Filtering->Filtering", but only then.

Also when using:

• "Filtering->Vapoursynth->Color" use the "Vapoursynth Preview" in the lower right corner (upper button) to preview the effect of your changes.
  
• "Filtering->Avisynth->Color" use the "Avisynth Preview" in the lower right corner (upper button) to preview the effect of your changes.
  
• "Filtering->Filtering" use the "Preview" in the lower right corner (lower button) to preview the effect of your changes.
  

Avisynth and Vapoursynth offer different color filters depending on your input one or the other might be more suited.

Cu Selur