I like the idea of swatching on smaller cards in sleeves like this, because you can arrange, rearrange, and sort as necessary, take them out if you need to, and swatch on different types of paper on the same page (e.g. if you need to swatch some colors on a black background)
This method probably works better for craft supplies than art supplies, where this might get bulky and expensive for swatching full sets of colored pencils, Copic markers, etc.
(For instance, crafters & journalers swatching white gel pens often want to know how they behave on black paper and over top of other media, like paint or alcohol ink.)
If Your Markers/Pens Are Dried Out
As you’re swatching, you may come across some dried-out markers or pens.