Re: two attributes with the same symbol in the map
Apologies if I'm misunderstanding you. I'm assuming these attributes are in the same layer, or this wouldn't be a problem. Maybe what you're looking for is in the Symbology tab of the Layer Properties box. Select Categories - Unique values, many fields and you can symbolize by more than one attribute. You could show a circle for volume and different colors for color, for example.
Maybe that's what you tried, and not what you want. If what you want is, for example, to symbolize volume by a circle and color by the same circle, I guess I don't see the point. How would you know which is which when looking at the map?
If the attributes are not in the same layer, you'd have to join the layers to get them in one layer. You can't, afaik, make one symbol representing attributes in two different layers. Again, not saying that's what you want. Just trying to cover possible scenarios, since I may not understand what you're looking for.