I have just have my braces removed and noticed a few yellowish discoloration on my teeth. Was that due to the braces?

These yellow patches are usually the result of poor tooth-brushing during the course of orthodontic treatment and are not related to the braces alone. If food debris and bacteria are allowed to accumulate around the tooth surface for a long period of time without removing them, then the acid produced by the bacteria will damage the tooth surface creating tiny holes. Overtime these tiny holes will trap food debris and turn white or yellow. If the tooth-brushing continues to be poor, then the teeth will decay and fillings would then be required.