That is just superstition. The idea that black cats are bad luck is a myth; there is absolutely no truth to it. I have a black cat, which means she crosses my path about 90 times a day. And my luck is no worse than anybody else's.
black cat and the red eyed black cat [only in the japanice area]
a black cat crossing you path
A black cat would be more unlucky than a white cat. An example of this would be the belief that a black cat crossing your path leads to bad luck. There is no bad luck that a white cat would give you.
The common superstition is that it is bad luck if a black cat crosses your path. This belief has origins in early European folklore where black cats were associated with witchcraft and evil spirits.
Superstition has it that a black cat crossing your path is an omen of ill fortune.
Most of the countries in Europe.
a black cat crossing the path brings bad luck small ears indicate that the is stingy
Not walking under ladders not crossing the path of a black cat Find a penny, pick it up
This very much depends on the culture. In the USA it is thought to be unluckly to have a black cat cross your path, whilst in the UK it is considered to be very lucky indeed.
Skrock (Swedish) is an omen or taboo. Sometimes it means magic or myth. For example. A black cat crossing your path.
a black cat crossing the path brings bad luck small ears indicate that the is stingy
I've heard of a black cat crossing your path to be a sign of bad luck, but I've not heard anything about black and white cats. In any case, it's just superstition, it doesn't mean a thing.