Blue Elijah grass

I have one in a 9" pot outside. I have brought it in for winter protection. It seems to have pushed itself vertically out of the pot, leaving four inches of brown, maybe bottom leaves that have died.

I want to repot this plant into a larger pot. What is the best time? and do I sink it into the new compost to cover the "dead" area. Will it go blue again in spring? thank you