I have a custom 3 colour diverging palette (red, amber, green) which I use in 3 steps. I want to add a 4th colour (a neutral grey) and have 4 steps. I have created a new custom palette and added a fourth step. However, despite using the same hex codes, the 3 original colours are different with 4 steps ( a lot more dulled and grey). Is there a way to keep the hex colours exactly as I have entered in my preferences?
I think what you want is the Use Full Color Range option. There is a good explanation of the Tableau color palettes and how to control them here: https://www.interworks.com/blog/rrouse/2014/12/15/understanding-sequential-and-diverging-color-palettes-tableau
I hope that helps.