You could use dual axis: in the same sheet, you create another graph like the one you already have, but instead of using those colorus, you should use a colour palette that goes from white to black (or light gray / dark gray). Then you activate the dual axis and adjust the transparency.
I would request you try the below approach.
1) Create a combined Field of two dimension
2) Press Control key and select (Dimension 1 say Region and combined Field Region+Category) and drag simultaneously to color shelf.
Adjust the color code or select the color code based on color pallete like dark to gray
You will able to see the desired result, please let me know if you still face issue.
Thank you Rajeev, this works!
Hi Willem, thanks, I have been trying that method but it always replace the current dimension (State) which have already been set as colour. So each time i try to drag the product to colour, this Product dimension always replace the State dimension. Is it possible to work around this? If this works it will be a more straightforward solution.
PS I notice your screenshot is slightly different to mine, I am currently still on Tableau 9.2.7.
Hi Rajeev, like Willem's response, I am unable to add two dimensions to the "colour" box. I have currently combined the state and product dimension and am manually changing each category colour. Please let me know if you know of a fix for this. Thanks!