The example that comes to my mind is a pile of wooden blocks. If I was asked to sort them I sort them by shape (i.e., by category). Here is a pile of the square ones, here are the circle ones, etc.
If I was sorting lego blocks I don't know if I would do it first by color and then by size/shape (here are all the 2x8s, here are all the 1x4s, etc.), but it would definitely be by category.
lego is funny, if you have a pile of red 'stuff' it's hard to pick out the 2x8. however, if you have a pile of 2x8s, it's really easy to pick out the red one.
This is a well known idea in data visualisation -- first articulated by Jaques Bertin back in the 60s (I think). Colour is known as a selective visual variable; selective variables are better used to represent categorical data as they "enable us to immediately isolate all correspondences belonging to the same category". i.e. sort your lego by bricks type rather than colour, though sorting by colour will lead to more instagram likes :)
If I was sorting lego blocks I don't know if I would do it first by color and then by size/shape (here are all the 2x8s, here are all the 1x4s, etc.), but it would definitely be by category.