Theme colours appear blank on block, why?

I'm trying to set a gutenverse button to the colours of my theme but when editing, the colours of the theme don't appear, it's just blank, why is that? Here is a picture to clarify. (my theme has a mix of blues and yellow).

https://preview.redd.it/0403nfr50lrd1.png?width=530&format=png&auto=webp&s=c1ccac3edf80e2e93ea70a07164b7915713d01c9