I don' have access to Tableau tight now, so I can't send back a worksheet, but I should think a simple calculation as below should work:
[Colour me red?]:
[Number3] < 0
This is a boolean. Drop [Colour me red?] onto colour. Then click on colour, select black for false and red for true.
Thank you Tim. What function is this? Could you please give me the full function. When I add this to the calculated field, it gives me an error -Syntax(maybe you are missing an operator).
In answer to your question, the function was a boolean function. This returns either true or false. I simply dragged this onto colour.
However, my first solution wasn't quite complete as it formats the whole row:
Clearly not what you wanted. Unfortunately, it gets quite a bit more complicated if you want to format columns of text independently. I found this description of a method for accomplish this by Kristi Morin: https://adswerve.com/blog/how-to-independently-conditionally-format-table-columns-in-tableau/
Once I had done all described there, I ended up with:
This is close, but not quite there as the headers are now at the bottom, so I also removed the headers, created a new sheet just with new headers in it and combined them in a dashboard to get the result you're looking for (needs a bit of tidying, though!)
I hope this gets you where you need to go. Sorry that it is more complicated than you were probably expecting. Any questions, please let me know.
Thank you Tim. That works.
If it did the trick, please mark the answer as correct as it helps others with a similar problem to find it.
Opps - you'd already done that!