Firstly, you cannot expect your staff to wash your cloths and secondly even if they agreed you would always wonder are they being washed correctly and all at the right temperature and with the correct detergent etc, etc. That said you need to sort that yourself.
Buy the Microfibre and glass cloths in bulk and yes make sure they are colour coded to what you want. Then when they collect from you, the next time they drop off the dirty ones and collect clean ones surely? It all however needs costing out accurately it may cost more to wash and dry them than to supply new as you have added labour, electricity, detergent and your time washing and drying
Hope this helps
Kevin