Is there any sort of colored transparent film w/adhesive that could be used on the lenses to "customize" a lense color?
Perhaps with some trial and error a whole range of color combinations could be achieved for every car and listed on your site. i.e. - VW New Beetle = light blue + this brand and item # adhesive film...
Of course applying the film properly would require a steady hand but hey you could even do it for an extra fee..
I dunno if this would work, but it might help a few people..
-John M