If you're extremely concerned about color, you can always order a color wheel (I'm not sure about amphigory, but most online wig stores have them...) Like Koumori-san said, you shouldn't have to be too nervous when buying the wig; for a character like Vash, you can really choose from a broad spectrum (anything from lemon yellow to golden blonde, though golden blonde usually comes out a bit dark in wigs... I would suggest a natural light blonde for that.) You can trust the color references, as the real wig colors only vary a small amount, (a wig color may look more vibrant or light, etc.) so don't let it scare you too much... (plus, if you are not satisfied with it, methinks Amphigory has a return policy.)
The Enchantment wig doesn't have bangs and the layers on Vash's hair, but there is a tutorial on amphigory about cutting bangs, so you can easily use that as a reference... (cutting the layers won't be a challenge either... when I cut bangs, all I need to do is copy the methods my hairdressers use, which always comes out with a great result ^_^)
I hope this helped and good luck on your wig search!
My new marketing ploy:
Michela: "I'm planning to place scorpions in my next costume, so that I can approach craftsmanship judges and say, 'not only did I hand make the entire dress, but I also added scorpions into the lining. I walk carefully when I wear it because I never know when they will strike. They are crawling around somewhere in the hems as we speak...'
And the judges will reply, 'SCORPIONS, YOU SAY? HAVE A TROPHY.'
Victory will be mine."
Ali: Scorpions are the new beading!