Lately anime production companies have been employing high dynamic range colouring to comply with the self censorship laws in Japan. Whether or not this is to avoid breaking the law or to encourage DVD sales is however, left to question.
Perhaps the large amount of bright light is to illustrate heavenliness of the experience...
Perhaps there are also reasons why angels glow a blinding white: to enable them to stay modest whilst avoiding having to actually wear clothes.
Though what place modesty has in this show is quite disputable...
Then again, the extreme brightness seems to make sense in an environment where the sun is shining brightly. Perhaps they know that kids are watching TV late nowadays too, and the brightness is here so as not to taint them.
But what are we to do when the subject being covered is a child herself...