Prime Colors

I cannot copy nature in a servile way; I am forced to interpret nature and submit it to the spirit of the picture," wrote the French painter Henri Matisse in 1908, looking back on a decade in which he and his friends had revolutionized image making.

Many of the results of that revolution can be seen at the Royal Academy in London, where 86 paintings and seven sculptures from the collection of Gabrielle and Werner Merzbacher are on show until mid-November.

The Merzbachers, both German-born, moved from the U.S. in 1964 to Switzerland, where Werner,...