Why does that coral look different?

I take pictures at different times of the day, and corals don't always look the same. Recently someone said the image (above) was bluer than they were used to seeing.  I took this picture around 9:30 p.m. when my reef was in a deeper blue hue.  

Had I taken pictures earlier in the day, the subject would have more white spectrum since that's a different look that I enjoy. I shoot what I notice when I notice it, which can be during about six different color spectrums daily.