Green ones are only used for decorative reasons, so the suppliers may make fewer green cords thus driving up the price.

It also could be that they want to clear the shelf space of the orange cords, and for some reason they have more of them than the green once.

But of course, the store is business and they exist to make money.

While it probably is the latter; I remember when I worked for sherwin williams, green was one of the most expensive colored pigments.