Impression 5.7" light blue get displayed as green

[Indiana8000]

Hello,

My Impression 5.7" display light blue as green, all other colores are very good. I also tried the dither.py:

• fast method make a very large white area with some blue dots (realy uggly).
• slow method looks near identical as if no hitherdither is used.
• Saturation have no impact on the color change itself.

Any ideas what I can do to improve this?

This should be a gradiant from light blue to dark blue: