The colouring is beautiful :) I remember colouring in Illustrator being ridiculously hard, so am not surprised you had dramas XD Back when I used Adobe products and did lineart (so about a hundred million years ago XD) I used to do lineart in Illustrator because the vectors gave the nice smooth lines and then coloured in Photoshop because that was so much easier.

I had to look up what ash tree leaves looked like and they would definitely have looked good, but I do think for purposes of a logo it reduces to the black and white version and would resize a lot better with the leaves as they are so good design choice there ;D