None.
attrcolor attrib [attribute/color-modifier]
This command can be used to highlight attributes by changing the color of
the text. If the attribute attrib is in use, the specified attribute/color
modifier is also applied. If no modifier is given, the current one is
deleted. See the String Escapes chapter for the syntax of the modifier.
screen understands two pseudo-attributes: “i” stands for high-intensity
foreground color and “I” for high-intensity background color.
attrcolor b "R"
Change the color to bright red if bold text is to be printed.
attrcolor u "-u b"
Use blue text instead of underline.
attrcolor b ".I"
Use bright colors for bold text. Most terminal emulators do this already.
attrcolor i "+b"
Make bright colored text also bold.