Grey water is water from your bathroom sinks, showers, tubs, washing machines and excess water from your Domestic Grease Trap, it is not water with anything related to sewage.
In most cases it is not water that has come into contact with faeces, either from the toilet or from washing nappies. It is wastewater and considered to be a harmlessly recycled water not suitable for drinking.

Colour

The color has nothing to do with the quality of the water and it can be used for various purposes such as watering plants, flushing toilets.
Grey water is different from fresh water and requires different guidelines for it to be reused.

• Don’t store (more than 24 hours). If you store this water the nutrients in it will start to break down, creating bad odours.
• Minimise your contact with Grey water which could potentially contain a pathogen if an infected person's faeces got into the water, so your system should be designed for the water to soak into the ground and not be available for people or animals to drink.
• Infiltration into the ground - don't allow it to pool up or run off (knowing how well water drains into your soil (or the soil percolation rate of your soil) will help with proper design.
• Pooling grey water can provide mosquito breeding grounds, as well as a place for human contact with grey water.

Here's the real definition of Grey Water - https://en.wikipedia.org/wiki/Greywater
Sources of greywater include sinks, showers, baths, washing machines or dishwashers.

Safety

As greywater contains fewer pathogens than domestic wastewater, it is generally safer to handle and easier to treat and reuse for onsite for toilet flushing and other non-potable uses.
Greywater may still have some pathogen content from laundering soiled clothing or cleaning the anal area in the shower or bath.
Treated greywater has a number of uses, some of which include toilet flushing or irrigation.