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