Kourtney tweeted about the colour of the dresses over the weekend, responding to a follower's question.
However, an insider told E! News that Kourtney's claims are "99% untrue."
The source explained: "The theme of the wedding will stay consistent with the invite."
The invitation requests that guests wear only black and white, which would suggest that the bridesmaids' dresses themselves are likely to be black.
Meanwhile, X17 Online reports that the wedding will take place at the Sotto Il Monte, a 10.9-acre mansion in Northern California. The estate in question was supposed to be the location of Jennifer Lopez's wedding to Ben Affleck in 2003, but the couple ultimately called off their engagement.
Kim will wed NBA star Kris Humphries on August 20 in California.
