This is a feature that would be really appreciated by artists as the purple/yellow colour scheme, while distinctive, is a lot less neutral than other websites and can easily clash with colours used in artwork. It may seem like a small thing but being able to choose the two colours that display on your profile and dashboard aside from the dark/light background would go a huge way towards making the site artist-friendly. There are equivilant features for twitter profiles and the default blog themes on tumblr, where you can select two or three highlight colours for your profile. It would also help with individualizing profiles a little at this early stage, without the effort of making them fully customizable. Though obviously they have their own issues, tumblr and deviantart are good examples of sites with neutral-ish colour schemes that lend themselves well to displaying artwork.
I noticed people suggesting this as a plus feature but I really think it ought to be considered as "basic functionality" given how strong and arresting is the default color scheme. I really hope it won't be considered "expanded customization" to be able to have a page that isn't burgundy, but I'm hopeful because the phrasing indicates plans for "non-expanded customization". Right now we are limited in what combos of icons and banners can we use to make a page look good (ignoring other formatting/design issues that I'm sure will be ironed out progressively), and for people who mainly post images it's a big deal because there are some kinds of art that can really loose out when displayed along such a forceful color
I say this as a person who plans on using cohost to post art going forward and wishes they could support the platform somehow but it is harder to justify when you're outside of USA/Canada/Western Europe/etc (any plans to accept one time donations or making some sort of micro/lite-plus-tier with less perks? it could for example only be available as a quarterly/yearly payment to not loose out too much on such small sums being processed every month)