I would remove the light as a whole, pull the bulb, and just start drilling. Remember to start small and work your way up in size. If it takes 4-6 drill bits, then so be it.

 

There are many other colors available at www.taillightking.com. Green, yellow, pale blue, rainbow...you name it.

 

Cool stuff - I wish I'd known about this place a couple of years ago. It would have been a lot easier to buy the 'green dots' (to match Hharry's flames) than to have to 'make' them.

BTW, it's not necessary to remove the taillight assembly to install 'dots'. I used a 15/16" paddle (flat) bit used for wood boring and a variable speed drill/driver. At very low speed, very light pressure, and very high patience, you can slowly 'machine' a perfect hole through the lens. A 1/4" to 3/8" piece of flexible plastic tubing taped into the end of a vacuum cleaner attachment will suck out the shavings. Clear silicone the 'dot' into the bezel and bend the tabs over to secure; clear silicone the assembly into the lens and clean off the excess gently with paint thinner (NOT lacquer thinner) on a soft paper towel or napkin.
Mine have been in for 2 years with no leaks. Hope this helps!