I recently cut into a russet and it had a long line of pink running across top. Looked like I cut it in half and ran a pink highlighter across the length about 1/4 inch from the side. Is that normal?

Most often, a pink or purple streak thru the potato is caused by cold weather during the growing season. Sometimes it is a potato reverting back partially to another variety that may have been crossed with the original at one point. Worst case scenario, is if the colored part turns soft, from a disease known as pink rot. This usually develops in affected tuber tissue when the potatoes are cut and exposed to air for 15 to 30 minutes.