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