If you can see the fish they can probably see you and in clear water they see the line and every thing else. They get kind of spooky and it is tougher to catch them especially when there is too much fishing pressure. You need to be very careful about what you are doing. I don't like clear water myself. As far as color I guess it depends on the river and I don't think there is a universal color.

Let me know via private message where you caught all your fish and I may be able to assist you further

Just realized that you were talking about sunny and not clear condition. I think under sunny condition they may feel more exposed as well because of the light. I personally like dark(er) days if the water is somewhat clear or dark(er) water if it is sunny.
My offer still stands