Found a site[1] that compiles SASS online. Correct results:

1. darken(#deadbe, 20) => #c16484

2. saturate(#deadbe, 57) => #ff8cb4

3. adjust_hue(#deadbe, 302) => #cfadde

All of these are much more reasonable results for these functions.

[1]: http://sass-lang.com/try.html