panel.isomeans(ybar,
lty.iso=7,
col.iso='darkgray',
lwd.iso=1,
lty.contr0=2,
col.contr0='darkgray',
lwd.contr0=1,
...,
col, lwd, lty ## capture potentially ambiguous name
)
col.iso
and lty.iso
.mmc
for the references and examples.