Raw/DNG files wouldn't be expected to work because they're raw; in other words the raw data has not been rendered to final RGB colors so Adobe Color wouldn't be sure what color rendering it should assume to build a palette out of. You may have applied some color edits to that raw file, but the data only lives in the Lightroom cloud database, not actually in the file itself. It might be possible if they built the Adobe raw rendering engine into Adobe Color and also set up a way of transferring edits from Lightroom through those files to run throught that engine, but that isn’t how it works currently. Currently Adobe Color is set up for fully rendered images such as JPEG.
So what should you do? When wanting to use a raw/DNG image in almost any raw editing software (not just Adobe software) with an application or website (such as Adobe Color) that’s expecting a finished image, you just need to export a copy to a rendered format such as JPEG. Export that copy to a normal folder on your desktop, then from there you can drag it to the other app/website and drop it there.
It’s an extra step or two but it has to be done. It's exactly the same reason photos uploaded to typical web galleries aren't raw/DNG; the software running the photo galleries expect fully rendered final images. Raw/DNG images are also not accepted by page layout, word processing, and video editing applications; they all want fully rendered image formats.