Blue edges around cursor only on external monitor.

[dflux]

I've seen the reports of blue cursors in case of the Intel gfx, but i'm using the current macbook pro 15" with a AMD Radeon, which i also confirmed to be the active one right now (gfxcardstatus).
On the retina screen of the macbook everything is fine but on my external screen, the cursors have a blue edge and also some other graphics in the the browser look like the are blue where transparancy is used.

Any ideas?

[dflux]

Interesting observation: if i set the resolution of the external display to 720p, the blue edges are gone. Not a solution to use it @720p but might be useful info for debugging it.