Orange food coloring substitute?

At a pinch you could use a little beet juice and some saffron (soak the strands in a tiny amount of hot water to extract the colour) - the red plus yellow should give you a really bright orange. Otherwise, try to get hold of golden beets to mix your icing.

Thanks for the help!

Turmeric turns everything bright orange.

Can you find annatto? That's what make Cheetos so bright ... it's a seed (or powder)

Kabocha purée and make a cream cheese frosting?

You could try some carrot juice