occurred on zsh-5.0.7 and older but I don't have zsh-5.0.7 handy to test on.) Evidently, the issue was due to elision. This addresses #665.0 and #665.5.
zsh-syntax-highlighting / highlighters
Navigate into the individual highlighters' documentation to see
what styles ($ZSH_HIGHLIGHT_STYLES keys) each highlighter defines.
Refer to the documentation on highlighters for further information.