The subject is pretty self explanitory, but why are temples so incredibly illuminated? Just to make them pretty? Some other reason they don't tell anyone else?
Because the devil can transform himself nigh unto an angel of light. Therefore it is no marvel that his Fraudulent Fifteen constantly try to depict the house of the devil as a house of light wherein are performed false, vain, and foolish ordinances that are absolutely NOT from the Lord. This is called "The Whited Sepulchre Syndrome."
The walls are painted a pale yellowish color which glows in that special Norman Rockwell painting way when lights are reflected off that color. It provides that "white and delightsome glowy" look. But really I like Canadian Friend's answer lots better.
Once after we had a blackout in our area, a rumor was going around the ward that the temple lights had miraculously remained on! Of course much later on checking out this rumor could find no evidence whatsoever ...