Just sometimes is best, I think.

Either the things wouldn't be so pretty, or our eyes wouldn't see them so well after a while.

But see, Cheri, the trees are growing common-coloured again, and Houpet is stopping.

We must have got to the end of the Forest of the Rainbows." "And where shall we be going to now ?" asked Hugh.

"Must we get out, do you think, Jeanne?
Oh, listen, I hear the sound of water! Do you hear it, Jeanne?
There must be a river near here.