How to override standard-css from the "fresh"-file?

Hi there,
i know, this has not much to do with zenophile itself, but as you brought up that idea with the "fresh"-css file, i'll ask you (and others) now:

i liked the idea to have a clean css file to be able to track my own changes and additions, but now found out, in opposite to what i expected, that i'm not able to overwrite the css of the main files from there.. which would be great, cause then i would just have my changes separated from the original and not having to "out-comment" the original code and add mine to be able to redo my trial-and-error work quickly.

tried to figure out myself how to tell the template to use my fresh file for overwriting existing css, but with no success so far.

can anyone give some hints to the clue-less css-noob please?