حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ لاَ تَبْتَاعُوا الثَّمَرَ حَتَّى يَبْدُوَ صَلاَحُهُ وَتَذْهَبَ عَنْهُ الآفَةُ قَالَ يَبْدُوَ صَلاَحُهُ حُمْرَتُهُ وَصُفْرَتُهُ ‏.‏

Ibn Umar (Allah be pleased with them) reported Allah's Messenger (PBUH) as saying: Do not buy fruit until its good condition becomes clear, and (the danger) of blight is no more. He said: Its good condition becoming clear implies that it becomes red or yellow. Translation Not Available

Book Ref: Sahih Muslim Book 21 Hadith 3667
Web Ref:  Sahih Muslim Book 10 Hadith 1534 c