How do I choose random things with custom values? (Inform 7)

Question

So I have a color value defined as follows, with some basic setup information. This is just a test for my curiosity, not any larger project.

Color is a kind of value. A thing has a color. The colors are red, blue, and black.

The Chamber of Secrets is a room. The chair is in the Chamber. The chair is black. The book is a red thing in the Chamber. The chess set is a blue thing in the Chamber.

And I would like to choose a random color, and then a random thing of that color, like so:

Every turn:
let hue be a random color;
say "You see [a random hue thing]."

I have tried several variations on this, and it works if I use a specific color instead of hue. (e.g. a random blue thing). How can I fix this?

Answer 1

The quick fix is to change a random hue thing to a random thing that is hue. Silly that you have to do that, but it seems to work.

But I'd recommend defining a relation instead, so it'll be clear what the connection is between hue and the thing:

Coloring relates a thing (called T) to a color (called C) when the color of T is C.
The verb to be colored implies the coloring relation.

Every turn:
    let hue be a random color;
    say "You see [a random thing colored hue]."