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