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