"We are constantly reviewing and advising as things change," she said.
Barnes said the report would go back to ministers "in the next month or two".
Bishop said the review was "good".
"Omicron has clearly changed the game and our settings have to change too".
Health experts including epidemiologist Michael Baker have previously called for a review of the traffic light system.
Baker has previously said it was time to "move on" from the traffic light system, calling it "far too crude" for Omicron.
"Omicron will behave very differently; it needs a different set of interventions to dampen transmission.
"Every single one of those pillars needs to change for Omicron. That's by far our biggest threat. Everything needs to be revised to deal with this new virus that behaves quite differently."