Why does it get crumbly when I add coloring? Its not stretchy to begin with too much. Should I have added more gelatin?

I'm no expert, but could you have added too much powdered sugar. I've made the recipe once and had no trouble. Maybe if you kneaded some more shortening into it as you work in the color, it would smooth out.
That's my best guess! Good luck.

Are you adding your color into the melted marshmallows? That's what I do.

Youcan't really add more gelatin. Try adding a bit more shortening and some glycerine.

oops I meant to say glycerine. It just crumbles when I add color. Is it supposed to stretch ? IF so how much?