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