Batman massacre gunman James Holmes has appeared in court in Colorado with bright orange dyed hair.

Holmes sat wide-eyed and appeared dazed as the judge in Denver advised him of his legal rights.

The court heard he will be formally charged next Monday with the murders of 12 people at the Batman film premiere.

The 24-year-old former graduate student is refusing to cooperate with police, and it could take months to learn what prompted Friday's attack on moviegoers at the midnight screening.

Investigators say they found a Batman mask inside Holmes' booby-trapped apartment.

Holmes has been held in solitary confinement since Friday. Prosecutors say they may consider the death penalty but will make that decision after consulting with victim's families.

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