The answer is yes.
Suppose you have a list in column A and another list in column C.
Highlight column A, so that A1 is the active cell and click on Format
| Conditional Formatting. Choose Formula Is rather than Cell Value Is
in the first box and enter this formula in the next box:
=NOT(ISNUMBER(MATCH(A1,C:C,0)))
Then click the Format button, then the Patterns tab (for background
colour) and choose your colour. OK your way out.
Then highlight column C and repeat with this formula:
=NOT(ISNUMBER(MATCH(C1,A:A,0)))
The highlighted items are not in both lists.
Hope this helps.
Pete