All of the data available on those sites for sovereigns is part of the Boundlexx API, which is a player-created API.
Color data specifically is collected when someone with the BoundlessProxyUI app installed and connected with an API key accesses a world. They don’t necessarily have to visit the world, just look at a portal to the world.
The list of available colors is updated when someone with the BoundlessProxyUI app opens up any world control.
There are webhooks available for getting announcements of new sovs, exos, and color unlocks, but getting that set up is fairly technical.
A simpler answer is to find a Discord server that already has a bot set up for this. I’m sure there are others, but there is one in the Boundless Modding Discord server, which is otherwise effectively inactive.