Conditional Format Matrix to Red/Black

1) Create a Matrix visual by going to Build and clicking on the Matrix Icon
2) Enter a value into the Values field
3) Click on the Format Icon
4) Choose Cell elements

Turn Font Color (or other option) to "On" > Click on the fx icon


Choose Rules from the "Format style" dropdown (see screen shot below)
Choose "Values and totals" from the "Apply to" dropdown
Keep the "What field should we base this on?" dropdown as is.
Rules Value Options:
1) Choose greater than ">" from the 1st "If value" dropdown. Go to the next field.
2) Enter a very large negative number, e.g., -100000. Go to the next field.
3) Choose Number from the dropdown (see Note below).
4) Follow the screen shots below for the other Rules values.

Note:  There seems to be a glitch in how the “Apply to” dropdown and the “value dropdown” interact.
If the 3rd field of the Rules dropdown (1) does not show "Number" as a option, change the "Apply to" dropdown (2) to "Value only". 
"Number" should now appear as an option in the 3rd field of the Rules "If value" dropdown (1).
Change the 3rd "If value" dropdown (1) to Number, then go back and change the "Apply to" dropdown (2) to “Values and totals”.