repairing my old robe

My beloved robe is wearing very thin in places, near the shoulders especially. 

Yesterday I laid it out on the floor to draw a pattern piece for the top part; the "skirt" is fine. It's a soft, dusty turquoise color which I couldn't match, so I bought some yellow - it will have to be two-tone. It's nerve-wracking to have to do this. I hope it comes out well!