[Geany] how to change syntax highlighting color for multiline comment block

[luca at email.com]

Hi guys,

I succeeded in installing set_geany_colors tool and change the syntax 
highlighting color of geany
in a satisfying way according to my taste except multiline comment 
blocks

example
<<COMMENT
this is
a multiline comment block
hello world!
COMMENT

this will be highlighted in violet on violet/light-gray background
I cannot find how to change this.

Even changing the colorscheme by loading any other conf file using 
set_geany_colors
Any color will change but not this one.

Which is the key to add / change?
I took a look at the manual without luck!

Thank you for any help
Cheers
Luca