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.