15w - what shape of lamp in question but important to know is not a normal wattage for as called a ceramic coated or otherwise inside frosted lamp from a premium brand in colors.
Can have your lamps dipped, or otherwise have to move up to 25w, or down to 11w. Halco
http://www.halcolighting.com/ and Bulbtronics
www.bulbtronics.com are amongst many - good suppliers of such lamps.
Otherwise, Midway is a manufacturer that makes 11 Watt S-11 shaped lamps - available thru Bulbman and most other normal lamp supliers. Midway is a good company for colored lamps. Action Lighting would also be a good supplier specilizing in smaller wattage colored lamps.
http://www.actionlighting.com/index.asp (Again - most lamp suppliers above and beyond the above sources can get either S-11 or S-14 lamps in 11w, 15w possibly with some effort, or get the lamps professionally dipped for you. Such dipping is possible dependant upon how dogmatic the 15w need is and bulb shape is, it's possible with some lead time to get the lamps dipped for you - won't cost an arm and a leg but will take a bit more lead time.)
Avoid dipping the lamps yourself - nasty stuff the Rosco lamp dip, but if you do, make sure them lamps are absoluetely cleaned or you will get oil from the skin problems. Even after this, nasty stuff - some experience with this stuff.
Another option is to do clear 15w lamps and something like #16925K22 from McMaster Carr
http://www.mcmaster.com/ which is a colored slip on safety sleeve for a A-19 lamp.