Using flow control
The major household companies around the world use liquid colourants (dye) for adding colour to their products. These colourants are very concentrated and often only a small amount is needed to give the required colour to the end-product. They do not add anything to the cleaning properties; however, it makes the product more attractive, and it will help to recognise a certain brand.
Especially the major brands place great value on consistent colouring of their end-products. Therefore, repeatability is of major importance, to make sure that there is no colour difference between the flacons on the shelves. Another important characteristic is accuracy. Since the colourants tend to be rather expensive, it is very much desired to dose as little as possible for optimal effect. The more accurate the dosage, the less colourant will be used, thus minimizing wastage.