How does plasma make a campfire flame orange​

The de-excitation of plasma (charged gas) is not the source of the light given off by a campfire's flame. The incandescence of solid soot particles billowing up on an updraft of hot air is what creates the light seen as a flame. Let us look at the typical ways materials emit light and then apply it to the campfire.
Electrons in molecules can exist in various orbital states. When electrons absorb energy, they are lifted to a higher energy state in the molecule. This is roughly similar to lifting a ball onto a high shelf where it can fall back down from. The absorbed energy of the electron is stored as potential energy as it sits in the higher energy state. Many things can excite an electron in a molecule to a higher energy state, including chemical reactions, collisions with other particles, and absorption of light. Eventually, excited electrons fall back down to their lower states, like a ball on a shelf rolling and falling back to the ground. When the electrons fall, their potential energy is lost and given off. There are many ways that a falling (de-exciting) electron can give off its energy, but the most common way is for it to emit a bit of light called a photon. As a result, any process that excites electrons leads to light being created when they de-excite. Often, this light has a non-visible color or is too dim to be seen by human eyes, but the light is still being created.