The spectrum, or color, of the light can vary. Also the focus of the beam can be different.
I don't like to use colored bulbs for tortoises. I prefer "white" light, or "sunshine" bulbs for day time and darkness at night. For animals that need night heat, I use heat sources that give off no light.
If your florescent tube is a UV bulb, and you feel it is working, then a standard flood bulb from Walmart or any hardware store should suit you just fine. To get your temps right, either adjust the height or the wattage of your bulb. I like to have a few around I case one burns out. Lowes has a pretty good deal on a six pack of 65 watt floods right now. This size works well for my applications.
During fair weather, outdoors is best, btw. But these bulbs should get you through the winter. I see a Russian in your avatar. Is that the fellow we are talking about putting lights over?
Is it normal for my tortoise to always sleep in the same corner on the cool side. Is it too warm? It's about 83 degrees on the warm side and 70 on the cool side.