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