Crooks was angry prior to Candy coming in, but had begun to calm a bit after talking with Lennie. Crooks actual takes no issue with Candy being part of the conversation, although it had been their dream to share their own ranch. Curley's wife is the one that "reanimates" crooks anger as she begins to put down the trio regarding their deficiencies. When Crooks is reminded of his own skin color (thus becoming aware of his own lack of self worth) this sets him off again.
