Alternative dialogue words you could use instead of the word…

Plain

As an Adjective

Specifically meaning free from additions, or embellishments

Antiseptic

Oh Naturelle

Austere

Bald

Bare

Bleak

Clean

Conservative

Denuded

Divested

Earthly

Elemental

Forthright

Homely

Honest

inconspicuous

Modest

Muted

Naked

Natural

Plain vanilla

Quiet

Severe

Simple

Sober

Spartan

Stark

Stripped

Subdued

Toned

Toned down

Unadorned

Undecorated

Understated

Unembellished

unobtrusive

Unornamented

Unpretentious

Unsophisticated

Unvarnished