Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
quran:68:20

And it became as though reaped.  

So by the morning it was like the darkness of night, in other words, black.
القرآن:٦٨:٢٠

فَأَصْبَحَتْ كَالصَّرِيمِ  

{فأصبحت كالصريم} كالليل الشديد الظلمة، أي سوداء.