Black and white image?

I got this new 800mw vtx and after connecting everything up properly I check the image in my goggles and it's crystal clear but black and white? I read that sometimes it defaults to black and white in the dark but even outside on a sunny day it's still black and white. During the test flight the connection is very strong however.

I tried viewing the video from an old fpv monitor and weirdly I got the image in full color but only briefly. After about 20 seconds it switches back to black and white and I have to re-scan the channels to again get color briefly.

At this point I'm not sure what the problem is but I suspect maybe the antennas? Or maybe a combination of using cheap antennas with 800mw? What could cause a black and white video feed?

Any ideas would be appreciated, thanks,
Yeah I keep it simple and set all my fpv stuff to the same channel, even on the re-scans when it lands on the right channel it still goes black and white after.