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