Here's what I did for my DIY JDM Amber side markers on my EP...should work the same...

Go buy some RIT sunshine orange dye and mix it up really concentrated...I used like 1/3-1/4 of the amount of water they recommended for use on plastic. I put my ingredients into a small Pyrex bowl and put it on the stove over very low heat. I had just enough heat to see the mixture slowly churning. There was no bubbling or boiling at all. Make sure you use a vessel that will allow you to submerge them completely in the mix. I mixed them around with the chop sticks every 5-10 minutes for about 45 minutes. [Wash your hands after every mixing. This stuff will stain your skin.] I took them out of the bath and put them into a bowl of clean cold water. I let the water run over them until it ran clear. Let them dry before you install the bulbs and reinstall them on your car.


Left is a real JDM factory amber, right is DIY.