Not a chance that your breasts are making skim milk! What your breasts were producing was perfectly normal human milk- and it told the story of your day as well as you did. (and isn't it weird that we compare our own fabulous milk to a substance made primarily to feed baby cows - and think that that is normal, not our own milk)
The amount of fat in the milk remains fairly constant, but when your breasts are relatively fuller, there is a higher amount of water and lactose - so your milk looks paler/bluish. If you feed/express frequently your milk has a relatively higher proportion of fat, so it looks whiter - but if it came out of your breast it is perfect for your baby. You are doing great, don't doubt yourself