Is that true that the color of pure water in a white plastered swimming pool should be blue?

If I understand the question, the reason for the blue in the pool water is actually the reflection of the blue sky. You will notice on an overcast day you see the white of the plaster and no blue. After looking at some internet sources (probably reliable), I've found out that in large quantities pure water is indeed blue, due to stronger absorption in the red end of the visible sprectrum than in the blue and green bands. Here are some links: http://www.minerals.net/mineral/oxides/water/water.htm http://www.marine.usm.edu/syllabus/MAR602lecture4-2002.htm http://www.des.ucdavis.edu/courses/est116/116_04.htm Picture of SuperKamiokande being filled with pure water (as pure as viable for about 50,000,000 liters): http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/photo/normal.html (link to photos) http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/photo/sk_build44.jpg (photo) For the tecnically minded, I've found out another good link to this subject: omlc.org.edu This page has many links to data with absorption coefficient for pure water. This page comes from: spectra/index