I'm thinking of buying a car what do you think of this scenario?

Some colours are more popular than others and that is definitely reflected in used car pricing.

But you have nothing to lose in asking dealer A to try and match the price of dealer B. Just remember that both dealers do this every day and are well aware of realistic pricing, so if dealer A knows that car will sell at or close to the asking price if you don't buy it then you won't get much (if any) movement. But if there's no movement on the price you can at least try to make sure you get extras included like a full tank of petrol/gas.

Having bought a car last week after extensive searching to NOT buy a black example with a black interior, it's very obvious to me that at the current time black is a popular colour. To buy mine I had to fly for two hours and then get a ferry and then a nine hour drive home, but I did also save a couple of thousand £ by buying a less popular colour with a cream leather (less popular than black as it shows dirt and needs regular cleaning) interior.

most dealers will match or beat another dealers price. Despite the colors. Although they might want an extra $500 for red because its more popular. But, I'm assuming you are talking bran new.

are they equipped the same? If they are, tell them you are ready to buy now. They need to match dealer B