Works exactly like the Vanilla "Monochrome Logo" setting.
The “Monochrome Logo” setting in Minecraft’s settings menu becomes redundant.
If your modpack ships with a defaultoptions.txt from KubeJS, the "Monochrome Logo" setting will not apply on the very first launch. This lightweight mod fixes that bug.
In:
YourMinecraftInstance\config\fml.toml
Change:
earlyWindowProvider = "fmlearlywindow"
To:
earlyWindowProvider = "blackearlywindow"