Where is the color for highlighting text at nachting opening bracket defined?

Hello everybody,

I have adjusted the color-themes to my personal preferences by modifying the color-values in the
theme.txt and the default.xml-file.

There is one small thing left I want to change
If you put the opening curly bracket in the same line as the code the arduino-IDE is able to popup the content of this line

void PrintFileNameDateTime() {  //<<<<==== do you see the opening curly bracket here?
  Serial.println( F("Code running comes from file ") );
  Serial.print( F("  compiled ") );
  Serial.print( F(" ") );

if the first line of the function is not shown in the IDE-Editor

And you put the cursor right behind the matching closing curly bracket

The line with the matching opening curly bracket is popup up
But the backround-color gives a low contrast to the textcolor

Which item in which file is used to set this background-color?

best regards Stefan