LeetCode 785 Is Graph Bipartite? - The Color Array

You need to track each node's color. Create an array color of size $n$. What values should you use?

A common choice: $-1$ means uncolored (not yet visited), $0$ means first color (say, red), $1$ means second color (say, blue). Initialize all entries to $-1$. When you visit a node, set its color to $0$ or $1$. Check if it is $-1$ to know if you have seen it before. This array serves as both the color assignment and the visited tracker.