To…IF…COUNT or Match that is the question.

Are the names going to be in 1 cell separated by Commas or in adjacent cells?

Assuming your first entry for the name column is cell B2:

Select B2.
Choose Conditional Formatting>New Rule.
Select 'Use a formula to determine which cells to format'
Type in the formula: =COUNTIF($B$1:B1,B2)>1
Click on the Format button and then choose your formatting options (fill red for example)
Click OK and OK again to finish.

With B2 still selected click on the Format Painter. Then click on Col B (by clicking 'B' at the top). This will apply the formatting rule to the whole column for you.

Note this will work on the 3rd 4th 5th duplicate etc etc. and assumes the whole name is in the one cell.