Use signs to make it clear
Support your colour coding system with good signage (using images or multilingual text where necessary) to help make sure your employees use it correctly.
Use colour-blind friendly combinations
One in 12 men and one in 200 women are colour-blind. Use different shades and contrasts to make it easier for colour-blind staff to differentiate colours.
If in doubt, take a photo of the colours and convert the photo into black and white. If you can tell the difference, the shade differentiation is strong enough to work for your colour-blind employees.
Carry out the colour coding programme in full
Implement your colour-coding system within all the zones affected at the same time. For greater clarity, have a definite date for phasing out your old system, and a clear start date for your new colour-coded system.