Dye coming off or just dirt?

I had just hand washed my garment and when I was air drying it in the shower, the water that comes off is a slight black. Is that the dye coming off? Or just dirtiness. Should I be worried about the color?

I had just hand washed my garment and when I was air drying it in the shower, the water that comes off is a slight black. Is that the dye coming off? Or just dirtiness. Should I be worried about the color?