This seems like such a common sense thing - but I didn't think of it until just last year.  (This tip is most useful if you have an older daughter and a younger son relatively close in age). 

I have two children - a girl (7) and a boy (5).   Since I had my daughter first I didn't think ahead on colors, so when purchasing her winter gear I always bought purples and pinks (snowpants, boots, etc...)  But then as my son grew, and he needed winter gear - instead of handing down her perfectly good bibs and boots, and had to go buy boy colored ones.  (Okay I didn't HAVE to, but you see where I am going).

So I've started purchasing more neutral colors for my daughter (blacks, blues, etc..) that can be used for both!  This comes in especially handy for boots & snowpants since they seem to need a new pair every year.  It really can help save money and resources!  

I also might try using RIT dye to color the light purple snowpants a darker color.  If anyone has tried this with any success please let me know!

But in the end, my new note to self - Defer neutral colors so gently used hand-me-downs can cycle from daughter to son!