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