When you try to edit a less file on jedit, by default there is no color scheme at all, that makes editing css files extremely hard.

To change the way jedit color code the actual file go to “Utilities > Buffer Options” and on “Edit mode” select the color scheme to css.

If you don’t want to do these each time you edit a less file, lets tell jedit to treat *.less files as css files, to do this, “Utilities>Options” and then choose “Editing” on “Change settings for mode” select css, then uncheck “use defaul settings” and chane “File name glob” to “*.{css,less}”.