I have a 2005 Chevy Cobalt with fog lights, and they for some odd reason are glass projectors, from the factory.( I know they were probably made for halogen bulbs , but still) So I was wondering would 35 watt 3000K Hid's be good?
No. First off, the fog lamps should almost never be turned on. Even good fog lamps, which are quite rare, are of very little legitimate use to most drivers and should be turned off most of the time. They are for use in fog/rain/snow to help the driver see the edges of the road close to the car so he can creep along through the bad weather at very low speeds. That is
all good fog lamps are able to do, and most of the ones available as factory or optional equipment or in the aftermarket aren't even capable of doing that. Leaving the fog lamps on at all times does not really or meaningfully improve seeing or safety, though many people do so out of baseless belief that they can see better this way at normal road speeds in dry weather. See
this page for more information, and
this thread on here for data and explanation (starting at post #4).
If you were to make your fog lamps put out 4x their normal amount of light by whatever means, it would not make them better fog lamps. In fact, technically and legally they'd no longer even be fog lamps. They wouldn't be "auxiliary" lamps, they wouldn't be driving lamps...they wouldn't be anything-lamps; they'd just produce completely dangerous levels of glare for other road users (regardless of their aim) and they'd completely destroy your distance vision by flooding the foreground with light. If you're going to use your fog lamps in conditions that warrant it, make sure they're equipped with
only the bulbs for which they were designed. "HID kits" are
not an upgrade. In halogen-bulb lamps (any kit, any headlamp or fog or driving lamp, any vehicle) they do not work safely or effectively, which is why they are illegal. See
here for details. Also make sure they're
aimed correctly and equip them with good quality clear-glass bulbs.
As for "3000K", marketers make up all kinds of numbers (such as "2500K" and "3000K") to hawk various kinds of yellow lights, but fact is that color temperature is a descriptor of white light only. There is no valid color temperature for light that is not white.