I purchased a yellow Shoei RF-1000 helmet, when I saw how very noticeable the color was on a two-up bike - especially in traffic, among cages. The yellow is much more apparent than white. It's similar to the GL 1800 pearl yellow color. A lime-yellow color helmet would be even more noticeable - just not very color co-ordinated with your bike color, but would, at least, match a similar lime-yellow colored jacket. Remember, that the helmet OEM's do NOT recommend painting helmets, since, the paint solvents can reduce the impact resistance of the formed shell.
I have a Cycleport/Motoport Ultra II Kevlar (Kevlar/Cordura/Lycra blend thread) lime-yellow jacket and black pants. The quality is absoloutely first rate. The abrasion resistance tensile strength of the Ultra II "MESH" (lighter weight & cooler in high temps.) is extremely high.
As I have previously posted, my suit literally saved my a$$ during a 65 MPH dismount from a deer strike, when I slid, then violently tumbled along the highway.
One important suggestion is to frequently spray the yellow color (red & blue also) with 303 fabric protectant (or similar quality) to reduce significant fading from the sun. Mine is faded and has lost the brightness of the 'flourescent' appearance of the lime-yellow color.
I know the nay-sayers will argue that regardless of our attempts for better visiblity, we are still very vulnerable. I do agree, but why not give yourself a possible edge at being seen. Sometimes, we aren't hit because something attracted the cage's attention, but we'll never know how close we came to becoming a statistic?