One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6)(7,9)(8,10)(11,12)(13,14)(15,16)(17,18)(19,20)(22,25)(23,27) involution — undirected(5,6,9,7)(8,11,12,10)(14,18)(16,19)(6,7)(10,11)(13,15,17,20)(14,16,18,19)(21,22)(23,26)(24,25)(27,28)(1,2)(3,4)(5,7,9,6)(8,11,12,10)(13,15)(14,19)(16,18)(17,20)(21,23,24,27)(22,26,25,28)(5,8,9,12)(6,10,7,11)(13,16,17,19)(14,15,18,20)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.