Specifying color or multiple colors as an eval argument creates black outlines on the lines.
| eval color = case (
match(app, "dns"), "green",
match(app, "tls"), "yellow",
1==1, "red")
i don't have this app installed, so this might not work. i can't find much on the documentation for the app, but it does say color: The color of the arc in hex format (optional, default "#FF0000")
on splunkbase. have you tried using hex values?
I tested hex values shortly after posting this, using hex values solves the problem.
I am still getting single color if i use the query eval color=if(protocol=tcp,"#FF0000","#0000FF")