Mustard seed can be yellow, brown or black. Yellow mustard seed is used to make mustard powder and American-style yellow mustard. Brown mustard is used for European- and Chinese-style mustards, as well as for picking. Black mustard seed is common in Indian cooking, but may be hard to find in American markets. Yellow or brown mustard seed works equally well in this salad.
As with all dried beans and legumes, the cooking time for lentils varies depending on how long the lentils have been stored. The cooking time increases in direct proportion to storage length. Check lentils occasionally during cooking and remove from heat when they are tender to the bite.