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)(13,14,17,21,18,16,19,22)(15,23,25,24,26,20,27,28)(6,9)(10,12)(13,15)(14,20)(16,23)(17,25)(18,26)(19,27)(21,28)(22,24) involution — undirected(5,7)(6,10)(8,11)(9,12)(13,16,18,14)(15,24,26,28)(17,21,19,22)(20,25,23,27)(2,4)(7,11)(10,12)(13,17,18,19)(14,21,16,22)(15,25,26,27)(20,28,23,24)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.