Did you purchase a kit or did you purchase the floss and the other items separately?

Depending on who manufactured the kit, they come in different ways, and some of those are (probably most of them are) with unlabeled floss. The best way to separate your floss is in natural, bright sunlight. Pull apart the colours and double check them, then count the number of lengths in each group. The instructions that come with the kit should tell you which colours have which number of lengths, so that you can label them accordingly. When in doubt, pull out the chart and find an area on the pattern that has one of the colours in question, then find that spot on the cover photo for the kit and compare it with the colours you aren't sure about.

As a last resort, since I keep a full set of DMC, I will look for a conversion chart online and look up what DMC colour is closest to the colour I'm trying to sort out, then will compare that with the kit strands to see which seems to match the best.