It is narrated from Nafi' (may Allah have mercy on him) that it is reported from Ibn Umar (may Allah be pleased with them both) that he did not consider it objectionable whether the (camel's) right side was marked or the left side.
Hadith Referenceمسند الإمام الشافعي / كتاب الحج / 837
Hadith Takhrijاسناده ضعيف لضعف مسلم بن خالد ولعنة ابن جريج : اخرجه البيهقى 232/5 - وفي المعرفة السنن والآثار له (3281)۔