Solving recently a problem with coloured table and hhline, I found that, as the babel-spanish module makes > and < active characters, using codes such as \hhline{>{\arrayrulecolor{some colour}}--} doesn't work: the line remains black.
A workaround consists in inactivating these characters with \shorthandoff. However, the same type of construction in the preamble of a tabular environment does work, so I wondered whether it should not be reported as a bug in hhline.
Here is a very short code demonstrating this behaviour:
\documentclass[spanish, table]{article}%
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{array}
\usepackage{hhline}
\usepackage[table]{xcolor}
\parindent = 0pt
\begin{document}
Without \verb|\shorthandoff|: \medskip
\begin{tabular}{| >{\bfseries}cc|}
\hhline{--}
Some text & Some other text
\\
\hhline{>{\arrayrulecolor{red}}->{\arrayrulecolor{blue}}-}
\end{tabular}
\vspace{1cm}
With \verb|\shorthandoff{<>}|: \medskip
\shorthandoff{<>}\begin{tabular}{|>{\bfseries}cc|}
\hhline{--}
Some text & Some other text
\\
\hhline{>{\arrayrulecolor{red}}->{\arrayrulecolor{blue}}-}
\end{tabular}
\end{document}


bugwording because I didn't find the relevant wording, and no one ever pointed it. I meant that probably you didn't notice there was a problem, so didn't care for it. What puzzles me is there's no problem in the preamble of the table. – Bernard Jun 16 '17 at 22:08