It seems like you're asking about the substances responsible for color in placards. Placards are typically made of materials like paper, plastic, or metal, and their color comes from pigments or dyes. These substances absorb specific wavelengths of light and reflect others, giving the placard its color.

Here's a breakdown:

* Pigments: These are finely ground, insoluble substances that are mixed with a binder to create paint or ink. They work by absorbing certain wavelengths of light and reflecting others. For example, a blue pigment absorbs most wavelengths of light except for blue, which it reflects.

* Dyes: These are soluble substances that color materials by attaching to the material's molecules. They also work by absorbing specific wavelengths of light and reflecting others.

Here's an example:

A red placard might contain a red pigment or dye that absorbs all wavelengths of light except for red, which it reflects. This is why we see the placard as red.

In summary, the substances in placards that absorb various wavelengths of light are pigments and dyes.

Please let me know if you have any other questions!