"kastra" = blue/green ??? ... i don't even know what to ask, but it's confusing for me. (Was the creator of High Valyrian Daltonic?)
High Valyrian is designed to look like an ancient language, and color names were far less defined in many of those than they are now. The word for blue and green being the same is not that rare. Japanese, for example, has a word that means both blue and green, depending on the context.