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)(17,19)(18,20)(21,22,24,26)(23,27,28,25)(6,7)(10,11)(13,15,17,20)(14,18,19,16)(23,28)(25,27)(8,12)(10,11)(15,20)(16,18)(21,22)(23,25)(24,26)(27,28) involution — undirected(1,2,3,4)(5,7,9,6)(8,11,12,10)(13,14)(15,16)(17,19)(18,20)(21,23,24,28)(22,25,26,27)(5,8,9,12)(6,10,7,11)(13,16)(14,15)(17,18)(19,20)(21,22)(23,25)(24,26)(27,28)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.