I have colour synesthesia :).
Something like 40% of people have it in a small way.
If you’d like to check whether you are in that 40%, ask yourself “What colour is Wednesday?”
You will either have no idea what this question even means, or you will have a specific colour that comes to mind. The latter are those with at least a touch of colour synesthesia.
For me, numbers and letters all carry specific colours, shades and textures. Z is dark blue and velvety. No idea why, but it is.