How to change the border color of loop group in plantuml?

Question

See, I have a loop in plantuml

loop 
    etl -> kafka:
    kafka -> linda:
    linda --> kafka: 
    kafka --> etl:
end

Now I want to change the border color of loop group from Black to DodgerBlue, neither

skinparam sequence {    
    SequenceGroupBorderColor DodgerBlue
}

nor

skinparam loop {
    SequenceGroupBorderColor DodgerBlue
}

works, the documentation work of PlantUML is so poor, I can hardly find any detail things, how to deal with this work?

Answer 1

The following does work for me:

skinparam Sequence {
 GroupBorderColor #ff0000
}

and

skinparam {
 SequenceGroupBorderColor #ff0000
}

To get all possible skin parameters use:

java -Djava.awt.headless=true -jar plantuml.jar  -language

and browse through the result.

See http://plantuml.com/skinparam for a small (incomplete) description of the skin parameters.

Edit: My initial: "Looks a bit like the color mnemonics don't work (maybe raise an issue at https://forum.plantuml.net/ask)" is not correct. I must have made a typo somewhere. retried with the comment from OP and it did work with DodgerBlue.