The purple light might be a black light. It looks purple because of a filter layer that covers it to block out most visible light. I don't recommend them for chameleons. You need something like a Repti-sun 5.0 long linear tube light. Sunlight also produces UVB.
There are 3 types of UV light...A, B, C...long and medium and short wave. UVB is the one needed to induce production of vitamin D3 needed to use the calcium in the chameleon's system.UVB has wave lengths from 280 to 315 nm.
Do you know about supplements?
If I don't explain things so you understand them please let me know and I will try to be more clear. Language makes it hard sometimes.