Black dogs looking for a home tend to be overlooked by potential new families, in favour of different shades of fur.
Dogs Trust is keen to dispel myths about black dogs as part of 'National Black Dog Day'.
The website has changed its photographs of dogs looking for homes to black and white to highlight the issue.
The charity is highlighting the importance of finding a four-legged friend that fits into your lifestyle - based on their personality rather than their appearance or coat colour.
The photos on the Dogs Trust website go black and white | Image: Dogs Trust'Black Dog Syndrome' is a common and unfortunate trend affecting black dogs in rescue, with many tending to be overlooked for other colours of dog.
It is unclear exactly why this happens.
Some say it is down to superstition - many people associate black with evil or bad luck, like black cats - or the old wives' tale that black dogs are mean.
Or even the fact that black dogs do not tend to photograph as well as lighter-coloured dogs.
Head of operations at Dogs Trust, Karla Dunne, said: "Every dog has his day, so we are delighted to celebrate National Black Dog Day and highlight some of the amazing black dogs in our re-homing centre waiting to be adopted.
"We are always trying to promote our dogs and give them as many chances as possible to find their forever homes, regardless of their age, coat colour or breed."
Portrait of a Black Labrador in Andalucía, Spain | Image: Ben Welsh/Zuma Press/PA Images"Unfortunately, black dogs can spend longer waiting to be adopted and Dogs Trust has found in puppy litters of varying colours, lighter-coloured puppies are often booked for adoption first.
"It may be that that black dogs don't stand out due to their dark colouring in kennels so people may scroll past them when looking through dogs in need of adoption on re-homing websites."
Assistant manager of the Dogs Trust centre in Finglas, Eimear Cassidy, said: "We find that the black dogs don't actually photograph as well - so they don't stand out as much as your other brighter-coloured dogs: your Golden Retrievers, Labradors, things like that.
"People can walk past them and overlook them when they're in the kennels, more so than the other dogs".
"They're still the most beautiful, loving dogs, they still have fantastic personalities.
"It doesn't affect their breed or how they behave - it's all just down to looks, unfortunately".
