I think different years of IS300's had different fog lamp bulbs and housings. But I know mine has a yellow lense.
Did you find your yellow bulbs for your IS250?
The canadian ones got the clear lens/clear bulbs. not sure if it was trim related. i think 03+ were all yellow lens when they changed it to accept an H3 bulb
but for the 01-02 with the 9006 bulbs, you got either the yellow or clear.
I have the clear on my 02 premium package (full leather, 6 disc, moonroof, blah blah blah)
but i know of 2 guys who had 02s with leather/suede and no moonroof and they had clear lenses, clear bulbs as well. so i don't think it was trim level related.
i know marc_lexus_29 has clear lenses as well.