Why doesnt unity find Hsb color?

So i got this code because i wanted my object change colors in in a rainbow motion. But it gives me the error “The name `HSBColor’ does not exist in the current context” how can i fix that

   TrailRenderer.startColor = new Color(HSBColor.ToColor(new HSBColor(Mathf.PingPong(Time.time * Speed, 1), 1, 1)));

The Original code i Copied

 rend.material.SetColor("_Color", HSBColor.ToColor(new HSBColor( Mathf.PingPong(Time.time * Speed, 1), 1, 1)));

how can i get my code to work?

Were you meaning to use this: Unity - Scripting API: Color.HSVToRGB
Unity doesn’t have an HSBColor class. And the error tells me that you did not create this yourself.