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