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