I think you have blue plastics on your DT 125R but you would like to have black plastics. Rub them down with some 600 wet and dry. Wash and wipe over with a tack cloth. Spray with a plastics primer (Halfrauds do this) and then spray with a plastic paint. Lacquer if required. Can be done in a day and left overnight to dry. Pretty easy really if you use the right stuff. The good thing is, if it goes wrong, let it dry off. Rub down and start again.