Since you're new to it, be mindful that Tru-Color has a short shelf life. The plastic bottles are poor barriers to the acetone base solvent, and it evaporates surprisingly fast just sitting there in storage. My hard-learned advice is to only buy what you need for an immediate project and do not stock-up "just in case" or for future projects with uncertain timelines.
Um, I know this thread was about water-based paints, but since the stinky paints were mentioned (which is what I use), I would chime in.
I move all my Acu-Painit and Tru-Color paints into glass 1 oz. bottles. I currently still have a stash of Floquil bottles where I also add disk of thick aluminum foil as a seal (over the original cardboard seal). I then mark the paint level on the bottle along with MM-YY date to see if any evaporation took place. I have some bottles of Acu-Paint that are over 20 years old (and unopened for 20 years), and there was almost no evaporation of the solvent. Of course I also make sure the lip of the bottle and the seal are perfectly clean before I replace the cap after use. Then I shake the bottle so the paint will seal any possible gaps in the seal/lip area. Yes, that seems a bit OCD, but it works for me, and I don't mind spending the extra time that guarantees the paint will not go bad.
Oh, I also put in couple of glass beads (about 3/16" diameter) to aid in mixing the paint. Do not use steel ball bearings - they will rust in those paints (don't ask how I know).
