Your best bet is a red colored one that's specifically for heat. The first week, the heat in your brooder should be 90 degrees, so you need a lamp specifically designed for heat. If it's too cold, the chicks will have really bad pasty butt or can even die. You can find these lamps at any feed or farm equipment store. Always use red light on chicks because, unfortunately, chickens are mean and can and will kill each other if a peck draws blood. The red light keeps them from seeing the blood.
I need some information. How big is the brooder and how many chicks? What does the brooder look like? Is it in a climate controlled area where the ambient temperature is consistent or is it outside where you can have wild temperature swings? What are the ambient conditions? A photo may help.
The ideal brooder (in my opinion) has a spot that is warm enough in the coolest conditions and cool enough in the warmest conditions. With that type of heat (which has been successfully used for many decades) the brooder needs to be big enough they can get away from the heat and it needs to have enough ventilation so the far end can cool off. It's just as dangerous to have it too hot as it is to be too cold. If you can give them a brooder where it goes from too warm to too cool they can manage themselves quite well.
About the only thing I know about your conditions are that you have chicks of unknown age, maybe with a broody hen maybe not, and that you have a bulb (I'll guess incandescent) of unknown wattage. It's hard for me to give specific advice when I really don't know what you are working with.
There are a lot of different ways to provide heat. Thousands of years ago the Egyptians piped in heat from charcoal fires, some are still doing it that way today. Heat lamps and incandescent lamps have been successfully used for over a century. Heating pads and heating plates are pretty popular today. There are other methods. I don't consider any of these better than others, they all have their benefits, issues, and risks. If they are used properly they can all work.
Here's my notes on chick heat, hope something in there might help:
They need to be pretty warm(~85-90F on the brooder floor right under the lamp and 10-20 degrees cooler at the other end of brooder) for the first day or two, especially if they have been shipped, until they get to eating, drinking and moving around well. But after that it's best to keep them as cool as possible for optimal feather growth and quicker acclimation to outside temps. A lot of chick illnesses are attributed to too warm of a brooder. I do think it's a good idea to use a thermometer on the floor of the brooder to check the temps, especially when new at brooding, later I still use it but more out of curiosity than need.
The best indicator of heat levels is to watch their behavior:
-If they are huddled/piled up right under the lamp and cheeping very loudly, they are too cold.
-If they are spread out on the absolute edges of the brooder as far from the lamp as possible, panting and/or cheeping very loudly, they are too hot.
-If they sleep around the edge of the lamp calmly just next to each other and spend time running all around the brooder they are juuuust right!
The lamp is best at one end of the brooder with food/water at the other cooler end of the brooder, so they can get away from the heat or be under it as needed. Wattage of 'heat' bulb depends on size of brooder and ambient temperature of room brooder is in. Regular incandescent bulbs can be used, you might not need a 'heat bulb'. If you do use a heat bulb make sure it's specifically for poultry, some heat bulbs for food have teflon coatings that can kill birds. You can get red colored incandescent bulbs at a reptile supply source. A dimmer extension cord is an excellent way to adjust the output of the bulb to change the heat without changing the height of the lamp.
I find the heat lamp bulbs are too hot for a small amt. of chicks. I've use a 75 watt incandescent bulb, and keep a thermometer in there to monitor temps. If the chicks huddle under the light, they are too cold, if they avoid it, they are too warm.
There are alternatives to light bulbs, such as ceramic heat emitters aka reptile bulbs, these fit in your fixture as well.