When I think of blankets or afghan's I think acrylics. Red Heart or Caron are the brands I know. They are what my mom used and still uses. Some of my mom's crochet work is now over two decades old and still wearing/looking good. My mom made each of her children a graduation afghan. Then with she made afghans for each each of our spouses.
Less than two years ago I had to repair my wife's afghan because our (then) puppy had chewed on the corner (unless one of our children had nipped it with scissors). The hole was in a white stripe and I had some white acrylic on hand. I did some Internet research about repairing crochet and then I made the repair. The patch was difficult to find even though the afghan had aged and the two white yarns weren't a perfect match. The patch was made working with the tails/loose ends from the old yarn doubled up with a strand of the new yarn to bridge to the next tail. I guess that is what made the edges of the new "white" fade into the now "off" white of the old afghan.
Who ever said "Old acrylics never die" was right. You are more likely to find a close match to an old acrylic color. But just in case, my mom has now put balls of the leftover yarn with the afghans she has made for her grandchildren (my children). I guess she know if they get damaged I'll be able to repair them even after she passes on to the the next great adventure.