IIRC, dark purple is a larger particle size but don't quote me on this.
What was in that bottle before you poured in the colloidal gold? If it was used before, perhaps it wasn't washed out thoroughly enough or perhaps you didn't rinse it with a few 1oz or so changes of distilled water to make sure there's no chlorine in there. I don't recall if chlorine or other "tap water" components can do this but I'd be shocked if it was temperature.
Hopefully others will chime in on this.