Unable to Disable `colr` Feature With HarfBuzz Renderer From the `fontspec` Package

Question

I noticed that if you use the Renderer = HarfBuzz fontspec option, the colr OpenType feature automatically gets disabled. If you use the default renderer, the feature does not get enabled but you can manually enable/disable it. My problem is that I cannot disable the colr feature if I use the HarfBuzz renderer. I cannot use XeLaTeX instead of LuaLaTeX or the default renderer instead of HarfBuzz as a workaround, because those are needed for the font I am using, which can be obtained here.

\documentclass{article}

\usepackage[bidi = basic]{babel}
\babelprovide[main, import]{arabic}
\babelfont[arabic]{rm}[Renderer = HarfBuzz, RawFeature = -colr]{digitalkhatt.otf}

\newcommand\ayah{^^^^06dd}

\begin{document}

بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah١
ٱلْحَمْدُ لِلَّهِ رَبِّ ٱلْعَٰلَمِينَ~\ayah٢
ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah٣
مَٰلِكِ يَوْمِ ٱلدِّينِ~\ayah٤
إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ~\ayah٥
ٱهْدِنَا ٱلصِّرَٰطَ ٱلْمُسْتَقِيمَ~\ayah٦
صِرَٰطَ ٱلَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ ٱلْمَغْضُوبِ عَلَيْهِمْ وَلَا ٱلضَّآلِّينَ~\ayah٧

\end{document}

I expected the end-of-ayah symbols in the above image to be black, but they are coloured.

Answer 1

You can use RawFeature ={colr=1} to activate colr font feature, and to deactivate the feature just replace 1 with any other integer.

\documentclass{article}

\usepackage[bidi = basic]{babel}
\babelprovide[main, import]{arabic}
\babelfont[arabic]{rm}[Renderer = HarfBuzz, RawFeature ={colr=2}]{digitalkhatt.otf} %  RawFeature ={colr=3}
\newcommand\ayah{^^^^06dd}

\begin{document}

بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah١
ٱلْحَمْدُ لِلَّهِ رَبِّ ٱلْعَٰلَمِينَ~\ayah٢
ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah٣
مَٰلِكِ يَوْمِ ٱلدِّينِ~\ayah٤
إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ~\ayah٥
ٱهْدِنَا ٱلصِّرَٰطَ ٱلْمُسْتَقِيمَ~\ayah٦
صِرَٰطَ ٱلَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ ٱلْمَغْضُوبِ عَلَيْهِمْ وَلَا ٱلضَّآلِّينَ~\ayah٧


\addfontfeatures{ RawFeature ={colr=1}} % to activate colr feature


بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah١
ٱلْحَمْدُ لِلَّهِ رَبِّ ٱلْعَٰلَمِينَ~\ayah٢
ٱلرَّحْمَٰنِ ٱلرَّحِيمِ~\ayah٣
مَٰلِكِ يَوْمِ ٱلدِّينِ~\ayah٤
إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ~\ayah٥
ٱهْدِنَا ٱلصِّرَٰطَ ٱلْمُسْتَقِيمَ~\ayah٦
صِرَٰطَ ٱلَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ ٱلْمَغْضُوبِ عَلَيْهِمْ وَلَا ٱلضَّآلِّينَ~\ayah٧


\end{document}