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