Following on from my article below. Weezl commented that it can be done for 18p a day. So I contacted her for details. Here is what she supplied.
Cheapest way to get all five colours:
raisins 20g 1.3p
marrowfats 20g 2.24p
carrot 80g 5.46p
tomato puree double concentrate 30g 5.28p
onion 80g 3.04p
17.46p (current asda prices march 09)
Not that I would just eat 5 a day, I prefer to aim for 9! But at least each portion doesn't have to be expensive, if budgets are tight.