All input textures whose format is multiple channels will be processed as sRGB color space and if such platform has support. So make sure you created all multiple channels textures in sRGB. Otherwise if platform supports but input texture is not in sRGB, then textures will be displayed on screen with more brightness. But for a single channel texture i.e. luminance just create it in RGB color space.
Bitmap font is generated from reading .ttf file thus by passing calling convenient functions of KRR_TEXTURE's loading function, thus texture is not always treated as RGBA 32 bit.
Internal texture loader will try to convert surface format to ABGR by default with 8-bit each for each color channel. If you see weird color, try to swizzle R and B color channel on your input image asset. Example, compressonator cli has an option -doswizzle, this might be useful for you.