First, you must enable it in the feature.conf file before compiling.
Second, you must run ELinks on a terminal that supports 256 colours:
--enable-256-color.
Third, you must set the TERM environmental variable to xterm-256color
before running ELinks.
Although the Linux frame-buffer supports 256 (or more) colors, the Linux console driver does not; therefore, console applications are still limited to 16 colors on the Linux console, frame-buffer or not.