Here's something I posted to their blog and thought was worthy to repeat here:
I think there are some concrete things you can do to ensure that you get more proposals from women of color and that you publish more works by women of color:
1) At past conferences, publishers have offered sessions for conference attendees on getting published. What about working with some of the other publishers, at conferences Seal attends, to do sessions specifically for women of color on getting published and getting their proposals accepted?
2) Host receptions specifically for women of color, or make a certain time during the book exhibits a time that you publicize as being for women of color who have book ideas or proposals.
3) Invite women of color to be on your advisory board (and if you don't have one, create one). Ask them to help you identify writers and works for consideration.
4) Read women of color blogs. There are theorists doing work that rivals any feminist writing out there.
5) Consider the impact of your cover designs. I looked at the covers of several of your recent books, and so many of them feature a white woman on the cover. This sends a clear message about the content, even if the white woman on the cover doesn't accurately represent the content of the book. There's no special reason the covers have to be white women, is there?
Many of these suggestions will both help ensure that you get more proposals from women of color, and they will also allow women of color to network with publishers.