Some terminals can display text in only one color at a time. On these terminals it is impossible to display text with separate foreground and background colors, unless one of the colors is black. The termcap code OC (one color) tells the runtime system to use special color handling to accommodate a terminal of this type.
If this code is present in the terminal's database entry, the runtime system displays text using the correct color combinations set from COBOL, so long as either the foreground or background color is set to black. If neither the foreground nor the background is set to black, the runtime system displays text using the foreground color (the background color is disregarded).
To use this code, add it to the terminal database entry preceded and followed by a colon (:OC:).