The protesters - wearing 'Just Stop Oil' shirts - invaded the Sheffield stage shortly after play had begun on the evening session of day three.
One male activist managed to jump on top of a table during the first-round match taking place on live television between Robert Milkins and Joe Perry, knocking a couple of balls before unleashing a packet of orange-coloured dye.
A female protester was also stopped from interrupting the match between Mark Allen and Fan Zhengyi after a quick intervention by the referee.
Play was suspended as cleaners looked to clean up the mess ahead of any play continuing.
Seven-time world champion Stephen Hendry, working as a pundit at the event for the BBC, told of his shock at the chaotic scenes: "I have never seen that before at a snooker event. It's a first.
"It is scary. You just hope the cloth can be recovered from that. It caught us all by surprise and then this happens.
"For me, straight away as a snooker player I am thinking: 'Is the table recoverable?' We don't know what that is on the table."
The protestors have reportedly now been removed from the venue and play has resumed after a 45-minute delay.
