Try mixing some colour with the clear coat; thin it out with acrylic thinners to aid flow; use a #0 or #1 fine point artists brush; fill the scratch or chip with paint using several applications, allowing the paint to dry between applications; mix 50% acrylic thinners with 50% Prepsol (wax & grease remover), and using a small flat-faced hard rubber or plastic block wrapped in T-shirt material or similar, wet with the thinners/Prepsol mix and rub over the repair to remove excess paint; buff off residue with a soft cloth and allow to dry; polish with a fine cutting compound. With metallic paints you may never get a perfect match but it should be pretty good.
June 88 535iA, 173,000 km; Sep 00 735i 170,000 km