This is not really a tutorial, it's an insight on maybe how I work, and to ENCURAGE PEOPLE TO DRAW FROM IMAGINATION AND NOT FEEL STUCK WITH USING A REF WHEN DOING REALISTIC HORSES
So we start from the beginning, looking at horses, to understand them, their movement, muscles, body and colours. I see horses everyday, but not everybody does. YOU MUST TAKE THE TIME TO SIT BACK AND REALLY THINK ABOUT HOW THEY ARE BUILT
Without the skeletton or muscles horses would not excist, and they matter a lot how you should draw a horse, so here we start.
All horses has the same muscles and bones (except arabians that has an extra pair of ribs, they are awful I know), so you know how they work you'll get movement soon. I think back on the skelleton when doing the guiedlines to get proper anatomy, and on the muscles when "forming" the horse when colouring. But we'll get to that, know, just take some time looking at horses. There are alot of good pictures on google at the horse skelleton and muscles, mine are very rough, but then again some details are irrelevant when getting some skin and fat on it I did this because it's fun