I've got a set in my Mazda Protege5. I don't necessarily consider them to be an upgrade, but they work well enough. I installed them just because I had one burnt ut OEM bulb and thought they'd look neat. Definitely yellow.
The output of most factory foglamps is so low that they are largely ineffective for improving driver vision. The yellow lamps will improve your visibility to other drivers though which can be just as important.
I haven't checked the fog lamp aim on the Outback, but the Mazda was set very low, and that is typical. If you do try to adjust the aim, keep the hot spot below horizontal so as not to create glare for oncoming traffic. VERY IMPORTANT.