For basking spot? If so, just use the standard bulb. Cost is less, and the only benefit I have found with the blue bulb was to give a little more "natural" looking light when used with the tube UVB bulbs. By the way, there is a way to edit your post for spelling or to add something extra... after you post there will be an edit tab at the lower right corner. This allows you to go back to the post and fix stuff!
Mine seem to recognise the standard clear or soft white bulbs as a heat source better than the blue bulbs. That is just in my limited experience though.
Ditto. The objective is to mimic the light they're getting from the sun. Hense, a bright white/yellowish light and UVB, so your chameleon feels and sees the world around him as if he were standing outside as much as possible.