@ArtistErin Hi Erin, you will find it to be virtually impossible to get accurate or exact match color across digital platforms. And social media companies like IG and FB employ compression to images that are uploaded to their servers. Sometimes it changes the image slightly, sometimes more noticeably.
If you plan to make prints of these images, your best bet is to get your working monitor as close to color correct as you can. If you are only going digital, a color correct monitor will still help, but you are at the mercy of the compression algorithms. Fortunately, IG does have some editing tools to help with uploads, but it probably still won't be exactly what you see on your Cintiq.