And another blue shot :-)
This is a good friend of mine at the Geysir high-temperature geothermal area. (The picture was taken in 1987, mind you. :-D It is a scan from my slides).
There are many different geysers, pools, springs hot bubbling mud pits, steam vents etc. there.
This beautiful blue pool is not one of the extremely hot ones, though. It is just pleasantly warm :-) -And if I recall correctly, it is called "Blesi".
-And it really is this blue!!
http://en.wikipedia.org/wiki/Geysir
http://www.goiceland.org/geysir_01.html