This was a difficult challenge to work on... people's opinions differ on what the "complementary colours" are, mainly depending on whether they are working with a system based on Red, Yellow and Blue as their primary colours ("subtractive colour") or a system of Red, Green and Blue ("additive colour") as their primary colours.
For this challenge, I believe either system is acceptable.
Complementary colours are pairs of opposite colours that contrast strongly when compared to each other. The challenge called for two complementary colors to compose your photograph but your photo shows the blue of the sky and the greens of the tree, and does not give the effect of a single colour against its opposite (complementary) colour.
I think your photo is a great capture, but not of complementary colours. Sorry!