So red hexagons are generated with the generateShape() function using bgcolor=0xFFFF0000 ? (thought it was with the generate_mask() function)
If so you can see that your generateShape() function don’t work either. So it is definitively an issue with the flash bitmapdata fill function. Nothing we can do here… 
Just use one of the other methods I posted before to circumvent this bug
so it;s working. no idea why, It would be great to know.
i removed generate_mask function
create new class that extend my class HexUI that have the same function but draw on it self.
created new instance of new HexMask class and its working as expected !
no idea why, the only difference was function generate_mask was creating new Sprite() and draw on it instead of creating separate class that draws on itself. as You can see methods generate_mask and generateShape are the same, with one difference that generate_mask create new sprite in runtime.