Ok, so I'm on Adobe Photoshop and i go file > new... to open a new canvas but no colours work there is only variations of gray and when i click channels it shows ony 'Gray'.

Can anyone tell me how I can fix this? Thank you in advance! :)

if you open a new file you have an option called "mode:"
choose RGB here and you will have colors

you can also change the mode in an existing file- I believe it's the Image(?) menu, then Mode.

if I was at school, I would know what I'm talking about because I could check- the only experience I have with Photoshop is for the school paper, which pretty much consists of changing the mode on stuff we scan to grayscale :P

just make sure the mode is set to lab or rgb when you open a new canvas. if that still not helps, check your settings for everything you made.....
if you still can't figure it, feel free to ask me.

:hug:
Sinem