Ay, I understand your worry! Hindi ko makita ang picture mo, pero if your LO is spitting up with something unusual alongside it, like discoloration, mucus, or anything that looks off, it's really best to show your pediatrician right away para ma-check properly. Could be reflux, could be something else, pero doctor lang talaga ang makakapagsabi with certainty, especially when there's something extra going on with the spit-up.
In the meantime, try keeping baby upright after feeds for a bit and see if it helps, pero please get it checked out soon so you and papa can have peace of mind. You're doing the right thing by asking!