Just Before An Eclipse
What do you think of a Language class for speech patterns or accents? I have difficulty adding colorful language to my character's dialogue even if I can imitate anything else. I don't know how exactly it would be taught however.
You'd think this is where I'd step in and be like, "hey, I can teach that, I do that all the time!" but in reality I'm not sure if I can put my knowledge of this subject into a teachable format.
So instead I'll give advice, go watch foreign movies, watch foreign stuff on youtube, pick a language you like the sound of and study it enough to learn the general sentence structure of it and how they pronounce words. Then listen to people speak it.
While you do all this, mimic it, yes, sit there and talk to yourself. Recite every line, every word of gibberish they speak, and mold your voice.
Then you will be able to apply it to your characters.
This is how I go about it, and for some silly reason I have three active characters which speak in funny accents, Alyssa, D'cund and Sam.
Just be warned that it gets tedious sometimes maintaining those accents in writing, and in order to avoid inconsistency it's best to write notes on how your characters goes about saying things. Also remember that all of our languages fail when we are in heightened states of awareness, like stress, nervousness, aggravation, infatuation, elation; etc. So they will speak extra terri-bad when such events occur.
I'm pretty sure I could go on, but like I said, advice.
As for the last paragraph of yours; that's Vay's department.