When you add Optifine into a 1.10.2 mod pack with mapwriter, all the mapwriter maps lose their colors and turn to just green and black pixels.

try and disable fast rendering

Same problem. Fast rendering disabled, does nothing.

that probably is a optifine issue, the moment the block colours are generated the texture is still empty. even tho in normal forge game the texture should be loaded by then. try and disable optifine and restart the game.

if you really want to play with optifine, then let mapwriter create the block colours without optifine. and then enable the setting useSavedBlockColours. this will prevent mapwriter from generating new block colours

Actually, this is the content of my MapWriterBlockColours.txt.
That looks very incomplete to me. Could Optifine cause that?

FML startup log.

Tryd even without optifine and still black and green

Not sure if this will help you but when I add Journey Map into my mods folder it seems to correct the green and black texture glitches. Now my MapWriter minimap and full map are operating the way they should be. I even tested removing Journey Map and when I did the green and black texture glitches returned. Super weird but it works for me.