It encounters an error when I click Palette, it may not work on GBC game...
But wait, the color accurates to what? I saw an SDA video before, that color looks like VBA, not this, so I don't know the ACCURATE.
Can BizHawk add an option to change GBC color mode in future version, like GBC.emu (on Android)?
To an actual GBC.
From what I can tell from Wario Land 3 alone, the colours on the default palette (Gambatte's) are nearly identical to that of an actual GBC. VBA's default colour palette (VBA Vivid in BizHawk) is overly saturated. BGB's colour palette with the gamma set to 1.00 and colour set to 0.85 is nearly identical to that of Gambatte's.
(I'd take a picture of the GBC screen, but it's nigh impossible to get a proper picture)
Oh, by the way, clicking on "Palette" (in the settings) when I have a GBC game loaded opens the window just fine for me.