The three-letter word for light that is not "bright" is "dim." It refers to a low level of illumination or brightness, often creating a subdued or muted effect.
dim
bright
bright light bright light
ray as in a ray of light
air
pat
Bright Light
Another word for bright is shining or shimmering maybe that is what i think
A three-letter word ending in "ux" is "lux," which means a unit of illumination or light.
bright light
Tan is a light brown.
bright, light