Every project can set an accent color and a logo from the dashboard, right below the preview link. This is available on every plan, including Free.
The accent color takes a hex code, like #e8a33d, and shows up on your public changelog page, on each release's permalink page, and in that release's shared preview image. The logo takes any https:// image URL and appears next to your project name in the same places.
Leave either field blank to fall back to Buoylog's default look. Changes apply immediately, no republish needed.