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