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