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