it seems to me in order to get the purple people want, bulb builders simply need to put more blue and less red into whatever they use to color the bulb. when the light shines through it, most purple bulbs come out looking pink. there's a good reason for this, which i will attempt to illustrate.
check out this image:
The top half of the image is standard purple -- 50% red, 50% blue, half brightness. (The RGB values are 128/0/128). The bottom half of the image is what happens to that color when brightness is doubled -- my attempt to show what a bulb of that color looks like when lit up. "Lit purple" basically looks pink, which is also what we are seeing in the real world when most purple LEDs light up, and why we hobbyists are so often disappointed with them.
Now look at this image:
This is a very bluish-purple color, with twice as much blue as red (RGB value is 64/0/128, aka "indigo"). The bottom half of the image is that color with the brightness doubled, my attempt to show what a bulb of that color would like when lit. In my opinion, that color is closer to the shade we are looking for in our purple bulbs.
keep in mind it is impossible to "project darkness" so it's not actually possible to make a "dark purple" light. The current problem is not in its brightness vs darkness, but that manufacturers are using a hue that leans too much towards red, and not enough towards blue. that's why they look pink when lit.
I believe a more blue-purple bulb would make purple inserts look exactly like what people want.