Is this what you had in mind? Have created colours for some of your columns but you need to duplicate the calculated fields for the remaining columns and add them to your sheet.
Sorry for reviving an old thread, but how did you include "Multiple Fields" in the Color box? I can't seem to replicate what you did, although I'm probably missing something really simple. I tried shift-selecting the fields then dragging them to the color box, but that looked for all Positive-Negative combinations for all 4 measures then created colors based on that.
If you look at the Marks card there is a drop down saying 'More Fields'. This gives the list of all the fields Rainier has on his Columns shelf. It seems as though I've created a calculated field so that you can format each bar's colour individually depending upon requirements. Select the bar you want to drop the colour onto from that drop down list and then put the relevant calculated field on Colour. The 'Multiple Fields' you refer to is displayed because you have the 'All' card showing rather than individual ones and is automatically generated.
I hope that explains it but please get back to me if not and I'll do some screenshots.