Well not nessisarily. If the sun changes color, that means the color spectrum has changed. Color is created by light and is made visible by water. So I suppose hypathetically if the sun did change color it could alter the spectrum and change the way water reflects the light.
my oceans are a green hue up in washington but normally look grey! but no the ocean would not look yellow is the sun was to turn green, which is impossible. I suppose if you couldnt see normal colors like a normal perosn it might look yellow
No. the blue color of the ocean depends on the colour of the sky because it reflects in the water. So if a green sun would make a green sky, then the ocean would be green. The water in the ocean does not have a colour.
As long as the sky is blue, then the ocean is blue. :-)