The concrete guys around here call it "cream" that is troweled to the top to give you a good finish.......that "cream" will rise to the top when it's troweled at the right time.
Nevertheless, you did just fine for an equipment pad.
If it drives you crazy, there are some products you can buy that set up in 10-15 minutes and you can apply them with a putty knife for a smooth finish. You would likely have to paint it, then if you get OCD like I do sometimes.