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