Welcome wiskers!
You could have a couple issues. When you say it turned a grape color- do you mean pink, or the color of a white wine like a golden color? Some of the color could be from the variety of pear used. Some varieties get a red skin whn fully ripe and some of the pigment could have gotten in the wine as the pectic enzyme broke down the pears if they were in the straining bag in the primary.
It could also be some oxydation of the pear as it was prepared. The directions say to add campden as the juice is extracted. If it took a while to cut them up, they could start browning. I prefer to use a bit of ascorbic acid while preparing apples and pears.Follow label directions, but about 1/4 teaspoon for a 5-6 gallon batch is enough to help-naturally less for a gallon.
Despite the color, how is the taste?