"My shirts are not black."
Translation:Mis camisas no son negras.
The tip when I type "mi" instead of "mis" is "watch the gender" - but mi /mis aren't gender associated, they associated with the plural. According to http://www.studyspanish.com/lessons/possadj.htm "Mi, tu and su do not have masculine and feminine forms. They stay the same, regardless of the gender of the nouns they modify."