Sounds like a Koan. I’ve been thinking lately about the colour of water. The water in the seascape I’ve been doing is slate grey. Why do I think it should be blue? Any colour that we see in water is generally a reflection. In this case it’s reflecting the sky which is grey and overcast. In the photo this is based on it’s actually snowing, hence the grey sky. The low cloud and mist is interesting but I’ve had to put some blue in the water. I know I’m basing this on my ideal of water, but I think that others will also expect blue. I expect blue and that’s the most important criteria.