Number Pattern for Double to show Negatives in Red

[Nick_Murphy]

Can anyone suggest a means of displying negative values from my fields in a report (the field is a Double) in Red, leaving positives in Black. I had expected to see this as a pattern to select from as per Excel, but its not, and not being very technically adept I am at a loss as to how to achieve this. I had sourced some sample code from similar forum entries but the samples seem to only apply to Strings

 

Would appreciate some advice, thanks