also...work on techniques such as bending and VIBRATO. These are very expressive tools that mean you can wring every last drop of emotion out of that note!
As far as "coloring" the sounds, you could really explore the tonalities of modes if you want to get into that.
From a more creative point of view, as mentioned before...try and FEEL the emotion you want to get across and have it in mind the whole time you're writing/playing!
Good Luck!