My penis head was pink and i have recently noticed there are brown looking spots on it and i don't know when it occurred. what could it be?

Here are some ...: Such color change in glans penis may occur and evolve along lifetime most commonly resulting from estrogen effect from sexual intercourse. Largely, it's harmless as long as there is no elevation, irritation, bleeding, etc. To clarify such concern requires professional evaluation and exam with inspection & palpation after detailing history on its onset, degree, progress, etc. over time.