Question

usually why we do not see bright colours in dim light

Answer 1

It is because no reflection of light take place in dim light so No light rays are entre in our eyes.......
.Hope it is sufficient

Answer 2

we don't see bright colours in dim light is due to thr reason that in the dark room there is no reflection of light .. so no light rays will enter our eyes .....

HOPE IT WILL HELP YOU. ......