CORE kɔː/ noun (Important part)
The basic and most important part of something:
PREMIUM ˈpriːmɪəm/ noun (Extra)
An amount that is more then usual:
This is actually important to me as name gives an instant idea of what something is. Being a premium member made it seem like you had paid for something extra, which is in reality what you had done. Being a core member makes it sound like you are more important then the rest. Of course you can argue that without paying members, dA wouldn't survive, but that doesn't make it ok to divide the members into more- and less important members.
The COLOUR of if makes it stand out against the other colours used by dA when it comes to design. If anything it should have been made green and white like the logo of the site itself, connecting