there is a school of thought that coloured icons can be confusing as the colour can take precedence over the shape

the same shape all different colours - easy to differentiate
the same colour all different shapes - easy to differentiate
different shapes and different colours together, confusing

the smaller the icons become the more this is so; the brain goes for the colour first and can 'lose' the shape

so some will find it easier and some will not depending on their familiarity with the original and how well they differentiate the icons...