Ceramic heat emmiter or a heat panel. Neither produce visable light so you can't possibly mess up their sleep! Pro products makes really great panels and they last a LONG time compared to any bulb I have ever used .
Red bulbs are fine turtle won't be bothered. Heat emitters are better no light just heat and it uses less electricity. Also they last longer. Heat pannles are pricey but like above last long.
If you want to look into the enclosure use a red light if you don't wanna see them at night he's emitter. That's what I would do. Maybe wait till the red bulb dies then switch.
I don't like the colored bulbs. Tortoises can see a wider spectrum of light than we can see. If we can see it, they can too. I think it does mess with them and I won't use them. I know lots of people use them, so I don't think it's the end of the world, but I choose to keep them dark at night and use CHEs, radiant heat panels, or other heat sources that don't emit light.
I found that even if they see it it's not totally pitch black in the wild. And my box turtles almost always dig into the ground or use the hide. Either way tho
I don't have a problem with the light, I have a small night light in my warm rooms. I have just found that CHE's are way better for me. The red bulbs just weren't very dependable, and didn't last long at all. The CHE will last way longer.
I use a red lamp bulb as in the ones that people would keep for chicks or ducklings. It is warm but tends to dry it out (I make sure to compensate with making it rain often but its a constant then they have a day lamp too. i found it to be a beter deal then any petstore bulb