I need to get a value using multiple selections in a single cell.

First list will display a list like Red, Green, Blue, .... Color10. Once the
user selects one of these colors using mouse, the second list need to appear
against this color.
It is like
Red
Green-C2
Blue D2
White E2
F2
1. The user can select Green and D2. The cell will have a concatenated
string value of "GreenD2". D2 is the value from cell D2. The cell can end up
with any combination from the four values in first list and four values from
second list. How can I do this? Please help.

2. Is there a way to get cell value 'GreenD2 and BlueF2', by letting the
user select more than once for a single cell?
thanks.