Answer:
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.
Soldiers line up spaced with pride. Two long rows lined side by side. One sole unit can decide, if the rows will unite or divide.
My first master has four legs, my second master has two. My first I serve in life, my second I serve in death. Tough I am, yet soft beside. Against ladies cheeks I often reside.
I work when I play and play when I work.
I am the tool, for inspiring many. Buy me in the store, for not much more than a penny. Don't overuse me, or my usefulness will go.
I'm the source of all emotion but I'm caged in a white prison.