For my game, Group Therapy, players always roll four dice for everything. Each die represents a portion of their personality. The results of these rolls determine both success or failure and the manner of success or failure. It's the mechanic that popped into my head first and lead to the concept for the whole game, actually.

However, this would require two full sets of standard polyhedral dice, at minimum (three of the dice can be the same color, but not the same size, while the fourth die should be a different color, but could be the same size as any one of the other three). Optimally, each player would have their own two sets of dice, rather than sharing. That's a lot of dice. Ordinarily, I'd say to hell with it -- that's what my original vision was, so that's what I'm sticking with. Besides, what gamer doesn't have a pile of dice already?

On the other hand, the game has a decent chance of being played by non-gamers, so sticking with standard d6s might be a good idea. To convert my original mechanic to d6s would require large, multicolored pools of dice.

So, my question isn't really whether or not I should change to d6s (that's something I have to figure out on my own), but whether having to buy a bunch of d6s in four different colors would be as much of a barrier to non-gamers as having to buy two sets of polyhedral dice. Any advice or thoughts on this would be welcome.

I would have to say, yes. If the only question is whether to use d6's or multiple polyhedral dice, I'd say stick with your original idea. Polyhedral dice aren't difficult to find or obtain. Certainly no more difficult than a bunch of d6's in various colors. I don't think it'd be any less of a barrier with d6's than it would otherwise.

1. People who really like the idea of your game will buy extra dice if they need to - they're not that expensive or hard to fine.
2. Most anyone who's ever played D&D probably already has them.
3. If you'r trying to sell to people completely unfamiliar with RPGs then it might be a barrier, unless you package the game along with dice. Non-RPers won't necessarily even know funny-sided dice exist.

I'm more concerned with whether the the inconvenience of buying multiple d6s in different colors would equal or exceed the strangeness and unfamiliarity of polyhedral dice for non-gamers.

So, it's not really a question of availabity, but rather inconvenience vs. unfamiliarity.