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