Not sure if that would work practically in a workplace at the risk of certain colleagues then being branded as lepers & a two tier environment being created which isn't the best way for businesses to operate.
My workplace has now 'encouraged' policy for all colleagues to wear masks when in a common area such as kitchens, reception, toilets & basically everywhere apart from when you're sitting at your desk.
People who have a cold really shouldn't be in the workplace in the first place & should be encouraged to work from home if possible rather than risk spreading it in the office. This was an 'unwritten' policy pre-COVID times so as to not potentially reduce the workforce even further & really should be more of a stringent rule during a pandemic, since I think we're all now educated how transmissible respiratory diseases can be.