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