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