You can understand by computed properties:
The Lab is a room.
An element is a kind of value. The elements are cyan, magenta, and yellow.
A reagent is a kind of thing. A reagent has an element.
A reagent has an element called the secondary-element.
a reagent has a text called the comp-color.
the comp-color of a reagent is usually "[the composite color of the element of the item described and the secondary-element of the item described]".
Understand the comp-color property as describing a reagent.
To say the composite color of (E1 - an element) and (E2 - an element):
say "cerulean"
Rule for printing the name of a reagent (called R):
say "[the comp-color of R] [the printed name of R]".
The gel is a reagent in the lab. The element of the gel is cyan. The secondary-element of the gel is magenta.
Test me with "get cerulean".