I've done a couple with only one floss color. One was blue variegated silk floss on white - a sampler. I have to say that I like stitching with various colors better, especially jewel tones.
It's spring - do something fun with lots of different colors. Try as I might I cannot wrap my head around doing something Christmas themed or winter for that matter. I worked in the yard today and noticed that things were coming up and budding already. I love spring.