Colour Me In

I am grey, still on the page
Oh colour me in
Just an outline, sketchy but fine
Oh colour me inIf green is chasing the hills over miles
If blue is pursuing the sky
See if the red of your heart doesn't mind
Where you begin to colour me inSomething new and nothing to do
Then I'm just the idea
I must be real, 'cause somehow I feel
That I'm just the ideaLet's share the blue of the towering sky
The green of the hills that roll by
Leave the red of your heart to decide
If you cannot choose which colour to use