wider = L & R signals sound different from each other
so processing L & R channels separately will produce wider
simple EQ with different settings on left and right can work
delays should work too (maybe try short delay times and/or delay time modulation)
or pitch shift L & R to make them slightly out of tune
there's a pile of dedicated stereo widener plugins, but personally not a fan, never use them
brighter/colder = frequency balance
so you can do brighter with EQ alone...
boost cold frequencies, cut warm frequencies, all done
alternatively, distortion/saturation that messes with the frequency spectrum how you need... tone knobs on distortion pedals etc
or layer stuff, i.e. make a copy of your initial sound, process to make it bright a.f. (maybe even pitch shift an octave up), eq out the lows,
then add what's left back to the original not-bright-enough sound to taste
or use a dedicated exciter plugin, of which, again, not a fan of
