It's definitely normal in bf babies. This is why my son's look like as well
It looks a little mucousy to me! It could be your babe is teething or not feeling well, or maybe isn't tolerating something you're eating as well as he could. It doesn't look like anything too serious though. As long as he seems content and doesn't seem to be in any discomfort, I wouldn't worry too much about it!
Are you eating a lot of fiber or greens? The consistency is normal. Until baby is on solids expect 'blowouts' like that Formula fed is more PB texture. But can always ask at next Dr visit/ talk to a lactation consultant through WIC or where you delivered