Customizable state-to-color mapping on default-card Slack notifications

The default-card Slack notification (via a NOTIFICATION policy's slack rule) already color-codes its sidebar by run state, e.g. yellow for UNCONFIRMED, red for DISCARDED, blue for CONFIRMED. We'd like control over that mapping, since blue doesn't read as "resolved" the way green would. Ideally either a way to set the color per state ourselves, or at least having Spacelift map CONFIRMED/FINISHED to green instead of blue.