This a good problem to have! The old "now or later?" dilemma. Spontaneous giving vs. milestone memento. I'm not sure I have an answer as to what I'd do. I tend to be a traditionalist and I work well with deadlines (like a graduation date) but I am also very mood-driven when it comes to my hobbies. I'm also TERRIBLE at waiting to give something I've made, so making it now to save for 4 years would not fit my personality. Besides, I don't want to hang on to things that could be enjoyed now.
As for colors, I'd make it in the child's favorite colorway but in a grown-up pattern. Most people who have a favorite color tend to keep it for a long time. I liked purple from age 9 to 49. I liked cool colors when I went off to college, but my aunt (who didn't know me well at all) gave me a bedspread in beige. Except for the turquoise bird on it, I hated it, but I felt guilted into using it. School colors didn't matter to me.
The older I get, the more inclined I am to give when the mood strikes, because as sushi said, there are no guarantees in life. But truly, it's a quandary. I'm sitting here trying to think what I'd do in your place.