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