How to format a negative number red within a mixed formula result

We use the following formula:

="Stu/W: " & TEXT((A$  2/B2),"[Red]#,###,##0.00") &"€" 

and wish to have the resulting negative currency numbers colored red and positive blue.

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Unfortunately neither this or other combinations we tried works. Neither did we find a solution using Conditional Formatting.
How can we have the resulting negative currency numbers colored red as well as the positive blue?