Asked by Judge Carlos Samour whether he had any questions about an 18-point advisement on the insanity plea given to him in court, Holmes said "No," The Denver Post reported.
Samour's ruling on the insanity plea comes after a weeks-long debate on whether the defendant should be allowed to change his plea to not guilty by reason of insanity. Earlier, a plea of not guilty had been entered for him by the judge.
Holmes initially asked to plead not guilty by reason of insanity in early May.
The Post said state law requires defendants who plead insanity to undergo an independent psychiatric evaluation that could require a transfer to the state mental health institute in Pueblo. An evaluation often takes takes months to complete. Trial is still scheduled to begin in February, but it could be delayed.
Earlier, Samour detailed consequences of a not guilty by reason of insanity plea.
Samour instructed both sides to be ready to discuss a possible waiver of privilege about a notebook Holmes sent to his psychiatrist.
Holmes is charged with 166 counts of murder, attempted murder and other crimes in the July 20 attack at the Century Aurora 16 movie theater. Twelve people died and 58 were wounded in the attack.