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