[tlhIngan Hol] qep'a' cha'maH wej mu' chu' - New Words

[Anthony Appleyard]

What does this word "chum" mean as a word by itself?

----Original message----
>From : mihkoun at gmail.com
Date : 16/08/2016 - 17:41 (GMTST)
To : tlhingan-hol at kli.org
Subject : Re: [tlhIngan Hol] qep'a' cha'maH wej mu' chu' - New Words

> {jajlo' chum}  sunrise (colorful sky) (n) (qep'a' 23 [2016], Friends of Maltz: Quvar)
> {tlhom chum}  sunset (colorful sky) (n) (qep'a' 23 [2016], Friends of Maltz: Quvar)

what's the significance of the "colorful sky" clarification ?
if the sunrise/sunset are taking place in a clouded/rainy sky, then
can't we use these words ?
....