I am just about to embark on a new book about colour and it’s a little terrifying because colour is such a personal matter. It not only varies from individual to individual, but different gardening cultures have totally different ideas. The Japanese love their restful green temple gardens. Launch them into planting up a container, however, and most will opt for the dolly mixture riot of colour. That’s something we restrained British tend to shy away from. South Africans are prone to mixing every foliage colour together, using silver, gold and rich-green in the same border. Strangely, it works with their higher sunshine levels – although I believe it jars the eye here.

I think most gardeners begin with a garish riot of colour like a toddler dabbling with paint. They also tend to plant their whole garden in the same way so sun lovers sulk in shade in some areas while some shade lovers crisp under full sun. Gradually the penny drops and over many years you learn to exploit your garden to the full by putting your plants where they are happiest. You learn that ferns and snowdrops appreciate deciduous shade. The leaf-green and virginal white combination looks freshly promising early in the year right up until the lily of the valley fades.

Transfer that bright-white and green theme to high summer, however, and the effect is much less pleasing. This was brought home to me by the old-fashioned rose ‘Madame Hardy’ (1832). This quartered stark-white rose, with a green button eye, was planted among other roses in glaring sun and it looked positively arctic – although it was fabulously cool in dappled shade. But the apricot-cream tones of the hybrid musk rose ‘Penelope’ appear to be a soft, silvered white under summer sun. Used above the pale-blue nepeta, ‘Six Hills Giant’, it creates one of the sights of summer.

I am still on the nursery slopes compared to some, but I have learned from other people’s gardens the importance of cool and warm colour and the effect of light. More than 20 years ago I visited a village garden which was entirely blue. I went on the Saturday, when the light was good, and enjoyed it so much that on the following day I took a relative. Unfortunately, the next day’s weather was sullen and grey – and so was the garden. A good scheme must work in all weathers and lights.

The secret of using colour well often lies within each flower. The blue geranium pictured, ‘Orion’, is the best summer-flowering strong blue geranium there is. It was brought to public notice during the hardy geranium trial at RHS Wisley (circa 2005) when it was clear to all that this one outshone all the other blue geraniums planted in close proximity.

If you look clearly at ‘Orion’ you can pick out a pinkish-mauve centre and purplish veins. These can be picked up by a red-toned plant like Knautia macedonica and the two shine together because their flowers coincide. The word coincide is vital here. There is no point unless they perform a duet together. So when it comes to matching colours examine at the detail, not the main colour.