I like this site a lot related to bulldog coloring, this breeder, writes articles from her experiences such as participating in UC Davis genetic studies on color, not here say they got from their show buddies who have a vested and financial interest in keeping the trends out.
https://rarebulldogs.com/the-merle-controversy
Can you believe the current trend in akc breeders of frenchies is to breed a brindle dog with as little brindling as possible, so maybe like one or 2 tiny eruptions of fawn on an otherwise black dog, however solid black is a disqualification in the akc (not the KC of England tho, I believe solid black and blue is acceptable there). Two alleles of the same gene, one is the most sought after, the other, breeders claim never existed in frenchies, and is a severe fault leading to disqualification.
In 2015 I think, the Bulldog Club of America voted to change the standard (not frenchies, but bulldogs, and frenchies have the same issues regarding colors and acceptance) so they can reprimand and fine judges who award a ribbon to a Merle dog of higher quality than to a standard colored dog of obvious poor quality based on other physical features besides color. So dogs who can barely make it around the ring they were breathing so badly or in so much pain, should be awarded over healthy dogs of Merle color. Some small shows may have very few entries, and judges sometimes have to choose “the best of the worst”. If that judge chooses a Merle over a lame dog the BCA believes he should be fined, rather than discipline breeders of unhealthy dogs who would go to shows with historically low entry to try to get a win for their lemon.
http://www.motherlodebulldogclub.com/whychangethestandard.html