The manual just says the wattage but not the type (such as an H-7). What sort of bulb is used in the headlight, and has anyone found a yellow one?

You can buy colored H4 bulbs from online or brick and mortar tuner car suppliers. Also a great source for silicone fuel and vacuum lines, in a variety of colors.  Also good for stick on fender/tank trim items. Look in the performance/tuner aisles at Pep Boys, they used to carry the same stuff for a lot lower cost.