Aspen…somethings

I have an Aspen tree in my backyard.  It is covered with these things, which I just researched, and found out they are called catkins.  Judging by the color of the catkins, this tree is a female.  If it were male, the catkins would have a reddish color.  Now why is it in nature the males are always the most colorful??  Regardless of the tree’s sex, I think they’re kind of cool.