I have three suggestions:
#1 is try to use one of those color pencils that are used on wood finishes that have scratches. I suspect that this solution has low odds of success, but it is worth a try.
#2 is a much better temp solution. The 99 cents store usually has felt tip coloring sets for kids, with about 24 different colors. With the variance in colors, you might be lucky to find one that matches pretty close. If you can't find a match, take a photo with your phone and go to an art supply store. They will have a variance of more than 100 alcohol based marker colors to choose from. Use the photo to match the color.
#3 This may work well if the cracks are actual splits in the material that will allow a filling to be pressed in it. Sometimes you can find stain samples at the hardware store. If you can find a matching color of stain, mix some of with Elmer's glue and then press it in the cracks. You can also try it with clear silicone adhesive/sealant. The 99 cents store has small tubes if the clear. A cheap buy so you don't have to spend $10 on a big tube at the hardware store. And one other base that can be used and mixed with the stain is a flexible putty filler.