the bottom line on staining a cloth or a towel by wiping one's hands on it; wiping one's hands on the same color towel;
Preparations for the Week: Different Ways of Handling Dirty Dishes and Cutlery on Shabbos;
Understanding the Difference Between טירחא יתירה (Tircha Yeseira, Major Exertion) and טירחא סתם (Tircha Stam, Minor Exertion) on Shabbos;