Some years ago I had a wall replastered and a new fireplace put in. The fire surround was attached to the wall and a white silicone used between the wall the fireplace. Since then, the plaster has dried or shrunk, so there's a small gap between the silicone and the wall emulsioned wall. What's the best thing to fill that with and be able to paint over if it isn't the same shade as the white wall?
