Pair duplicates are not marked in possible values display

[ghost]

Requirement 1.e.ii: If there is a duplicate value, the corresponding value should display red.
Expected: Possible values display's a duplicate in red.
Observed: Duplicate is greyed out.
Test Data: test_load_near_solved.txt
Steps to Reproduce:

1. Launch application
2. Load the test data.
3. Enter an incorrect value into the remaining space.