Green and blue and red all over

Here’s a little puzzle. (No prizes for the winners: just think of this as a pure mental challenge in which getting it right is the only reward you can expect. A bit like life, in many ways.)

What is blue, red or silver when it’s with glass and red, green or blue when it’s with plastic?

Well, you can pour it on your breakfast cereal, you can pour it into your coffee, and if you’re not looking what you’re doing you can even pour it over the cat. The answer, fact fans, is milk.

And those colours? They’re the bottle tops. Depending on whether you get your milk from your friendly local delivery operative or from the shop, it’ll come in traditional glass bottles or the squidgy plastic equivalent.

And if you get the former, skimmed milk has a blue top, semi-skimmed a red top and full cream a silver top.

But if you buy your milk in a plastic container, the lids are red for skimmed, green for semi-skimmed and blue for full cream.

If you want to live dangerously, there’s also gold top, that nectar of the gods which comes with its own European cholesterol warning and the childhood ingestion of which is largely to blame for your correspondent’s current stoutness. But we’re not worried about that at the moment. Much.

Now, it’s all very well if you only buy one sort of milk. But if you’re the sort of family that runs out of bottled on a Sunday afternoon and has to make a run for the shops, then come Monday breakfast you are in for chaos and confusion.

Because (just in case you weren’t paying attention earlier) glass skimmed is blue, plastic semi-skimmed is also blue, and glass semi-skimmed is red.

(Look, you were promised a mental challenge, and you’re getting one. Just hang on in there and there may be some kind of explanation later. Just remember that nobody said there would be a point to this.)

Right. Imagine for a moment that you’re on the sort of health kick which involves you drinking only skimmed while the youngsters get the semi-skimmed variety, and your mind is in its usual state at seven o’clock on a dark and murky Monday morning.

Blue? Red? Red? Blue? Glass? Plastic? Plastic? Glass? Arrgh.

It’s no wonder you’re grumpy by the time you get to work and decide to enjoy rich, creamy, non-healthy semi-skimmed in your warming morning beverage. And your grumpiness is not improved when you find the fridge at Chronicle Towers packed with plastic milk cartons topped with a bewildering range of red lids (skimmed) and green lids (semi-skimmed), plus the occasional blue one for those playing Extreme Artery Challenge.

There is a sort of serious point to this. And it’s not about the fact that the aforementioned fridge has recently been declared a Site of Special Scientific Interest.

Because all this labelling is pretty confusing even for those of us who aren’t colour-blind, and must be even more so for those who are.

Red-green colour-blindness is the most common form, blue-green much rarer. And what colours do those bottle tops come in? Red, green and blue.

Yes, of course you can read the label or the printing on the foil top – or at least you can if your hand is steady enough to hold the bottle still at the ungodly hour when you rashly promised to get up and make Mrs D’s tea.

But beware when you next open the milk: it could affect your blood pressure in more ways than one.