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