Hello Alekh,
That is not possible in the standalone version of WaterGEMS, you could to use the tools in MicroStation or AutoCAD to change the color of the label. You can try this with the program in that platform (WaterGEMS for MicroStation, for instance) or export the drawing to a DXF file by going to File > Export > DXF and open the DXF in one of these platforms.
However, we have filed an enhancement for this to enable changing color of the label to be different from the element color, the reference number is #127211.
You can add prefix or suffix to element label through annotation properties but putting underlines is not possible at the moment.
Could you please explain the reason behind this, so that if feasible we can consider an enhancement for this to be considered for the future release of the product.
Regards,
Sushma Choure
Bentley Technical Suppport