When you start YASARA under Linux and get the message

Disabled smooth atom colors because OpenGL extension XY is not supported

then your OpenGL driver is either very old or not installed properly. YASARA still runs, but it can display only the following atom colors: blue, magenta, red, yellow, green, cyan and gray, e.g. smooth color gradients will only be visible in ribbons and ray-traced output, but not in the individual atoms on screen.

This problem sometimes comes together with an error message about extension "XFree86-DRI" missing on display ":0.0" .