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