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