Hello ... you have 2 options to achieve that:
1. Use 3 label controls ( for each text row) and set the Color and FontWeight property of the "---Testfirma---" label according to your need;
2 Use a HtmlText control and on HtmlText property use:
"<p style='text-align: center;'>Der neue Kunde</p>
<p style='text-align: center;'><strong><span style='color: #0000ff;'>---TestFirma ---</span></strong></p>
<p style='text-align: center;'>wurde erfolgreich gespeichert</p>"
- please notice that I used quote(') and not double-quote (") inside Html code.
Personally I prefer the second choice to avoid load memory with 3 controls against 1.