One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(6,9)(7,11)(13,14)(15,16)(17,18)(19,20) involution — undirected(7,11)(10,12)(14,18)(16,20)(21,22,25,24)(23,27,28,26)(5,6)(7,10)(8,9)(11,12)(13,15,17,19)(14,16,18,20)(21,23,25,28)(22,26,24,27)(1,2)(3,4)(5,6)(7,10)(8,9)(11,12)(13,16,17,20)(14,15,18,19)(5,7,8,11)(6,10,9,12)(13,15)(14,16)(17,19)(18,20)(21,24,25,22)(23,27,28,26)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.