Sometimes an API isn't in Firefox or Safari because they believe that the feature is harmful, and refuse to implement due to privacy or security concerns, such as Web USB: https://mozilla.github.io/standards-positions/#webusb
Other times, Firefox and/or Safari are implementing or considering implementing it, and only Chrome has fully implemented it yet, such as the Badging API: https://mozilla.github.io/standards-positions/#badging.
@codestance, can you help make separate colors for these two cases?