Everyone thinking about 2-state vs. 3-state controls is automatically honoring the device's color scheme setting. The controls are an extra to let users choose to not use the device setting on a particular site.
Rather than each site making its own design for such a control, I wish browsers would make it a per-site setting users could use.
Rather than each site making its own design for such a control, I wish browsers would make it a per-site setting users could use.