Are you talking about changing to a different type of bulb or just a colored bulb?

I would leave the bulb at a 197 / 168 wedge and change colors but not go to a higher wattage that 5 or so. Too little room in there for adequate dispersion of heat.
There is a guy that made his own bright LED array in Japan and I copied what he did. I like the incandescent bulbs better. The LED's are too directional.