I am in the UK and have a pal Sega Mega Drive 1 that has been modded with a 50/60Hz switch. When I switch over from 50hz to 60hz, select back and forth on my switcher or go through the AV channels on the TV remote the picture after a few seconds suddenly gets brighter and more vibrant like someone has turned up the colour setting a few notches.

It will either do it when flicking the switch on the console from 50hz to 60hz or when and I select another channel on my switcher box or press the source button on the remote and get back to the Mega Drive. Basically whenever the TV decects the picture it starts off kinda dull then all of a sudden increases in colour.

I have tried the recreate this with my Super Famicom that has a switchless mod but no issue at all with the Super Famicom. I'm guessing it's comething to do with the TV adjusting to the Mega Drives video output signal? I would send a video but with the refresh rate of the TV its close to impossible to see it through a camera. Basically after I switch Hz or input after a few seconds or so the colours get brighter and more vibrant.

Can anyone offer any info on whats going on? Using a CSync RGB cable from retro gaming cables.