The Lincolnshire-based nursery, which supplies soft fruit plants to growers, has introduced the charts to growers and their customers to help both parties better understand how long a picked strawberry will stay a particular shade of red once it hits the supermarket shelves - and what that shade means in terms of taste and fruit quality.
Hargreaves said that the well-established French system has been used by the company's research and development department for several years but was introduced to growers and their customers after reports that supermarkets have this summer been rejecting Albion strawberries that are too dark.
He said: "One or two growers have had a colour issue. We know the variety to be high-yielding and delicious to eat. The only thing about Albion that was open to interpretation was its colour. So we addressed this problem.
"In the past four weeks we brought out the chart as a way of working with supermarkets and our customer base. The colour chart enables them to determine, for example, that a strawberry that is colour number two on the chart when harvested will become (for example) colour number four within three days after harvest."
He said that the chart has encouraged some growers to change their picking dates accordingly: "Working with that colour chart, growers - when the sun is out - have reduced the period of time between harvest intervals and are better able to harvest the fruit to the colour that is required."
He added: "It's in the interest of growers to get that right and satisfy their customers."