It is not the lightest orange tone, by far, and I do not have any trouble reading it on my monitor... Of course, it depends on you own monitor settings (if set too bright, it might wash out the colors and reduce their contrast).
Red is already in use for muted avatars, so it would be too easy to confuse both (especially when you do not have both types listed at once)...
Since there is no solution that would satisfy everyone in the world, I made the Radar colors (all of them) skin-able (i.e. defined in colors_base.xml for each skin, which you can override with your own <local_sl_settings_dir>/skins/<skin_name>/colors_base.xml file). It also makes them configurable via the Lua SetDebugSetting() function...