Nasai

574. Commentary:
This hadith is evidence that before the sun turns yellowish, while it is still bright and shining, voluntary prayers (nawafil) may be performed. The exception mentioned in the hadith «إِلَّا أَنْ تَكُونَ الشَّمْسُ بَيْضَاءَ نَقِيَّةً مُرْتَفِعَةً» "except when the sun is white, clear, and high" is valid and authoritative. From this, the hadith: «لا صلاة بعد العصر حتی تغرب الشمس» it is permissible to perform voluntary prayers after ‘Asr. This practice is also narrated from some Companions (radi Allahu anhum) and many Followers (Tabi‘in). For details of the hadiths and reports, see: [محلی ابن حزم : 2؍272 ، 275 ، وشرح سنن النسائي للإتیوبي : 7؍364 ۔ 372]
Therefore, it is not correct to declare this exception as anomalous (shadh), nor is it correct for the Hanafis to say that at this time only the "Bayda" (midday prayer) and similar prayers may be performed, but after the sun turns yellow, even these should not be performed. Moreover, there is no solid evidence for this interpretation, and this distinction proves impracticable in light of other general texts. In the hadith it is stated: «من نسي صلاة أو نام عنھا ، فکفارتھا أن یصلیھا إذا ذکرھا» [صحیح مسلم ، المساجد ، حدیث : 684]
"Whoever forgets a prayer or sleeps through it, its expiation is only that he should perform it whenever he remembers (or wakes up)." Therefore, whether the sun is shining or has begun to turn yellowish, in both cases the prayer may be performed.