Do some softboxes emit a warmer light than others or is it post processing

I've been looking at different combinations of strobe and softbox combinations used for portraits on Flicker and it seems some are warmer than others? Does the light modifier or post processing cause this warmness?

There will be a slight variation, brand to brand - and different flashes are slightly different colours (some change as the power is dialed up or down too)

Most of what you are seeing is likely gelled flash, or PP afterwards

I frequently use a CTO gel on my flash to balance with tungsten, or a 1/4CTO for a "late afternoon sun" look.
Ocassionally i will even use a CTB to cool down a rimlight or background light

Some strobes also have some constant color light, while others dont which means there could be a greater variation in light color.

And the 'white' polyester front panel will YELLOW WITH AGE...just like a cotton or blend white dress shirt in a closet, if hung there for years without laundering!

Furthermore, all light sources (different brands as well as different vintages of equipment) do not necessarily all have the same color temperature...even the same light at different power levels!

I'd say more than a little variation for sure between my Elinchrom, Fotodiox and Photoflex. Enough to not mix them for main and fill.

Still, I would submit that most of the noticeable variation is done in post.

If you shoot raw, you can do a test to see how the color varies by shooting a target with neutral greys, like a Macbeth color checker, then use the eyedropper in the raw processing program to get the color temp of the neutral grey.

If you don't test, you're just guessing.

I find, for instance, that my Softliters and Chimeras are fairly close to each other; the Fotodiox octas are perhaps 100 units cooler, unless I put in the inner baffle, then they're close to the others. A bare reflector is perhaps 100 degrees cooler than a softbox, but it varies with the box.

And as noted above, you will get color variation as you adjust the power on most strobes. I am usually using a strobe pack and head setup rather than monolights, so the color temperature of the lights is moving together and can be corrected for (the lights don't change in color relative to each other)

Some brands can produce considerably different colour temperatures with the same light source, in an ideal world try to stick with the same brand.