There is quite a degree of colour variation, which is probably the main reason for the confusion over species. Some males having orange cheeks, which is why "orange cheek Pleco" is another common name found in circulation. This is not made any easier by the fact that the fish will gradually darken if left in a tank with a darker substrate and lighten when kept on a lighter substrate. These changes take some time (hours or days) to effect, they do not happen quickly, so there is no real "chameleon" effect here, but no doubt it is a useful survival mechanism.