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