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