Many killies lives in areas where not much light gets through the water surface. Following light is not essential to killi tanks. Actually many keepers does even not have light on their tanks and use a torch when they want to see the fish clearly. But you can use all kind of light sources you want. Just remember to give the fish some darker hiding places if you plan to use strong light.

A common combination is ordinary light tubes like T8 or T5 and then combine this quite strong light with dense floating plants like Salvinia, Riccia fluitans, floating Egeria densa etc. This way you will have a good combination of plant growth which increases water quality, a great spawning material and good shadow for the fish.
I also use this combination and use a timer to turn on and off the lights at the same time each day. 10 hours of light - 14 hours of darkness works fine for me.

If you have a sunny room you can also just use the daylight. Only problem is that direct sun light has much power and could give you problems with algae. It is sad to have the most pretty fish in town and be unable to enjoy them. Some people can handle it without algae growth but I have never succeded in sunlight on my tanks without increasing algae growth.

But - buy yourself a good torch. When the tanks is completely dark and you turn on the torch you will see the most impressing colors. Killies are beautifully in the daylight (or tube light) but in dark surroundings with a torch light - the colors of the fish shows its real value. For many species you will be amazed. I guarantee.