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