Hi there!
The only issue I know with Visustella is that you need to go into the plugin settings for Core Engine, change Quality of Life Settings, then scroll down to the bottom to change "Font Width Fix" to "false" and it'll fix some text issues. Besides that one, I'm not aware of any other problem.
By using my Bitmap plugin, the colors will only change if using the Pro version. Regardless you have Visustella or any other plugin that changes text colors. Because these other plugins are made to change the color of the default RPG Maker text, which is not the Bitmap Text.
As you may know, Visustella plugins are obfuscated, but also, just a single plugin has a lot of features. Honestly, there is no way for me to check this out. So, besides the fix I tell you about above, I don't know if it will fix anything related to the visustella as you said.