Display issues with my TV/Mac Mini

I connect my MAC MIni to my LG TV via Onya Reciever, when i cahnge to PC input, from satalite, Blueray DVD or whatever i always get a poor colur dispplay, set to 60Hz and the colour is purpleish.

I have to toggle between optimise display and 50Hz several times before the colours finally match and i can view my mac and contents correctly.

I suspect its an issue witht he output through HDMI from my Reciever, but im hoping someone has similar and has resolved this issueß

Thxs