Why a rainbow? Because different colours possess different phytonutrients providing different health benefits. As a general rule, the most colourful fruit and vegetables are richest in vitamins, minerals and antioxidants.
Some vegetable types come in many shades of the spectrum; carrots, tomatoes, sweet peppers, radishes and beans. Lettuce comes in all shades of green, some with a red tinge. The shape and texture varies too. For a quick growing tasty addition to salad try a mix - baby salad leaf lettuce sown in trays or in a patch outside will be ready for cutting in a few weeks (watch out for slugs though!).
Radishes; black, violet, red, red/white, pink and yellow all have white flesh beneath their colourful skin. An unusual one is radish red meat which has white skin and red flesh. Summer salad varieties such as cherry belle, sparkler and blue-moon(pink) are mild in flavour and take about 4 weeks from sowing to mature to a size for pulling.
Beans too are easy to handle for small hands when sowing but will need some sort of support (a tepee of canes) to grow up. Not only are the beans themselves different shapes and colours from pencil thin french beans to flat runner beans and chubby broad beans, the flowers are pretty in red, pink and white and combinations in between. The pods can be green, yellow or purple, and speckled too.
Some varieties come in a ready mix; rainbow chard is shown. Rainbow carrots are also available.