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