SCNoChange stops syscolor from setting system colors on startup, but not from setting system colors from its bang command. (and I can see where that might make sense...) If you're making a theme, don't set the colors on startup with a bang command. Instead, set SCLoadSection to the name of the section to load from the ini file, without the []. (Is that even documented?)

Otherwise, Cerbie's idea is pretty good... might I suggest lsnothing?