If Colorado laws forbids refusal of a business service based on 'sexual preference' of the potential customer, as in the Masterpiece Bakeshop case, the bakery owners can be charged and fined. However, as The Blaze article points out, Americans have a constitutional right to the practice of their religion. The bakery refusing to bake a 'wedding' cake for a same-sex couple may be technically discriminatory but the real point here is to force acceptance of homosexuality down the throats of those who reject it and make the supposed 'right' of homosexual men or women trump that of those who disagree with their choices on religious grounds.
This was likely a well planned set-up as in a city like Denver, there must be plenty of bakeries that would make a wedding cake for anyone who had the cash. The cake isn't the point. Making homosexual behavior 'mainstream', by force, is. This should be interesting when gays try to force a Muslim business to service them in a way clearly connected to their homosexuality. Oh, wait, they won't. Muslims will burn your house down if you dare offend 'allah'. Christians politely refuse and face the legal consequences. Meanwhile, Americans keep having their individual rights abridged, by law. In the distant future, historians will have a field day examining the decline and eventually demise of America. This case may be an example.
It sounds like they deliberately targeted that business—undoubtedly they could have found another bakery that would accommodate them. Something very similar happened recently in the Portland, Oregon, area and was discussed here.