Hey Alex Martino,
I attached a workbook (Version 10.2.1) and a screenshot in case you cannot open it. The steps I used to color the bars are based on the exact same steps as the following Knowledge Base article: Show Positive and Negative Colors in Chart | Tableau Software
In case you need to re-create a Waterfall, here is another KB article: Creating a Waterfall Chart with a Second Dimension on Color | Tableau Software.
Let me know if it helped! Have a great day
Hi this is really useful. Do you have a workbook in version 10.1? Would really appreciate this. Thank you very much!