I read in Storey's Guide to Raising Ducks that a blue light is easier on ducklings eyes but it didn't say exactly what kind of light. incandescent, fluorescent, halogen? I have seen blue day bulbs at the pet stores for reptiles
The blue light spectrum is on the cool end. So you can buy blue bulbs or simply white bulbs. I would not use halogen, it is way to intense. Fluorescent does not emit heat, so it is out of the question for the brooder. I use standard white light bulbs in various wattage for the brooder. Be aware that blue light makes them lay larger eggs too, which is not always a good thing. I use a natural spectrum light in their duck house for the laying hens.
A more initially expensive but really helpful item we used was ceramic heat bulbs - no light, just heat. They come in different wattages. I had mine from a reptile I kept for 29 years. She passed away a few months before the ducklings arrived.