[vram22]

>final case object Red extends Color

On a side note, that syntax seems a little counter-intuitive - the extends word seems to indicate that Red is a subclass of Color, but from what you said seems more like Red and Green are values for Color. So it seems like an enum would be more appropriate here (for this use of Red, Green and Color)?

[dragonwriter]

A Scala “object” declaration declares a singleton; it's an object, but you can also define object-specific class features.

If the instances need behavior (which in practice they often do), this is useful. Presumably, in the example, they would in a substantive program, but the behavior is irrelevant to the illustration and thus omitted.

[vram22]

Interesting, thanks.