We know the process takes between 12 and 24 hours, but not how the different petals turn out different colors.
这一过程耗时12至24小时，但不同的花瓣如何呈现出不同的颜色，就不得而知了。
That remains a trade secret of their creator, Dutch florist Peter van de Werken, who branched out from creating brightly colored chrysanthemums.
这是发明者、荷兰花商彼得•范德威尔肯的商业机密。在培育出彩虹玫瑰之前，他还曾培育出了彩色的菊花。
He buys long-stemmed Vendela roses, dyes them and distributes them around the world. They still have their sweet smell and the flowers will last as long as normal roses, but the leaves may wither sooner.
More than a million were sold in a year, with key markets in Japan, Italy and particularly Sweden, where blue and yellow varieties mimic the national flag. Britons can buy them at online florist Interrose.co.uk.
