Calculation condition or conditional show with text box are the easiest solution, but if you really want it the way it is in screenshot:
Create calculated dimension: =IF(aggr(Sum(Approvals),YearMonth)=0, 'Nothing is approved', YearMonth)
Red color to text color: =IF(Sum(Approvals)=0, rgb(255,0,0))
Then we need two expressions with conditionals:
Expression: ' '
Calculated dimensions can sometimes bring performance issues.
in chart properties,general tab, under calculated condition write something like =If(sum(approvals)>0, 1, 0)
and then click on error message button in general tab, click calculation conditions unfulfilled, and write your custom message below.
see the attached example
Sales2.qvw 147.5 K