Sublime Text doesn't come with LESS highlighting by default, but it's quite easy to install.
I've pulled the following from my previous blog post on how to install Zen Coding/Emmet in Sublime Text.
The first thing you want to do is open up Sublime Text. If you don't already have the package manager installed, then install it by bringing up the console
'and pasting in:
import urllib.request,os; pf = 'Package Control.sublime-package'; ipp = sublime.installed_packages_path(); urllib.request.install_opener( urllib.request.build_opener( urllib.request.ProxyHandler()) ); open(os.path.join(ipp, pf), 'wb').write(urllib.request.urlopen( 'http://sublime.wbond.net/' + pf.replace(' ','%20')).read())
Press enter and wait for that to install. Once complete, press
Pto bring up the command palette and type
Install, press enter to select
Package Control: Install package.
Once the menu appears, type
LESS and select the first package.