Get your self some water soluable or permanent soft tip marker pens at your local crafts store. They come in multiple colors to a pack and run the gambit of the color line. A set of these marker pens will run about $4-$8 for the set depending on how many are in the set. They are soft tipped like a highlighter and you can blend the colors in depending on the shade you need. Black is the easiest to color in and I think blue is the hardest.
The chip in your piece, unless it is a major chip, should not take away from the value but if your like me I prefer no chips at all showing. If it doesn't bother you leave it alone, otherwise color it in and if you sell the piece later on let the buyer know that it's been touched up and let him(or her) decide if they still want it.
Rich