A FLUSH of green is spreading across the Arab world, but not because its vast deserts are shrinking. Green is the colour of Islam and Islamist movements have reaped the biggest harvest of the Arab spring. Not all stripes of Koran-led politics have flourished equally. In the Sunni Muslim heartlands stretching from the Atlantic to the Persian Gulf, neither violent extremists in the mould of al-Qaeda, nor proponents of Iranian-style theocracy, nor woolly Islamist liberals have fared especially well. Instead, the prize is going to groups linked to the centrist Muslim Brotherhood, committed to evolutionary rather than revolutionary change, and more concerned with questions of Islamic identity and ethics than with imposing rigid God-given rules.