Say Blue Realty is trademarked
Will Blue.Realty be a problem?
Yes.
Being that Both Blue and Realty are generic words
So are "Burger" and "King". Most trademarks consist of dictionary words. But there is no kingdom of hamburgers out there somewhere which is actually ruled over by a Burger King, so most people immediately recognize that word combination as a well known fast food restaurant.
Can I use "Burger King" for a plumbing business? No, but the better question is why would anyone want to do that?
What If I use Blue.Realty as a medical business? WIll it cause less problem?
Yeah, if I have a medical problem, I'm going to head over to "Blue Realty" to get it treated, because the name alone tells me those doctors know exactly what they're doing. Afterwards, I might even have lunch at Ace Sewage Service.
Trademarks exist on a scale of relative distinctiveness. Some marks are more "inherently distinctive" than others. Let's look at some potential realty business names:
Boston Realty
Town & Country Realty
Welcome Home Realty
Blue Realty
Booyanuts Realty
Those names are on an increasing scale of inherent distinctiveness. "Boston Realty" is pretty much a
generic term (it straddles the line between generic and descriptive, really) referring to realty in Boston. It is unlikely to be owned or used by any one party. "Town & Country Realty" is somewhat
descriptive - they likely deal in both urban and rural real estate, but it's not clear where. "Welcome Home Realty" is
suggestive - it is connected to the idea of realty through the phrase "welcome home" which is inferentially related to acquiring a home, but is not directly descriptive of buying one. "Blue Realty" is
arbitrary - the color blue is a dictionary word, but is arbitrarily applied to realty. Finally, "Booyanuts Realty" is what we call a
fanciful mark - "booyanuts" has no meaning whatsoever and is a word I just made up for this example. Fanciful marks are classically the strongest marks, because they have no meaning other than in connection with the trademark.
So, if there is a business out there called "Blue Realty" which is distinctively and substantially exclusively known as such, then using "Blue Realty" for something else would be kind of like using "Air France" as a brand of shoes. Not only does it not make any sense, but it is obvious that using "Air France" to sell shoes simply comes across as a shoddy attempt to make the ridiculous claim that you are not intending to evoke the goodwill and reputation of the airline for your shoe business.