Is it? I'm not trying to be argumentative, but I have never seen a "standard" colour belt system with requirements from the KKW. In my case, my first school required taegeuks 1 & 2 to obtain a yellow belt, whilst the next school required a "basic" pattern (taegeuk1 is taught at the yellow belt level).
Exactly. For Kukkiwon it's important that you meet their standards once you attending your first black belt test.
In the official WTF-affiliated organisation in Germany, Switzerland and Austria things are handled the following ways:
Germany: 10 Kups, 10th white, 8th yellow, 6th green, 4th blue, 2nd red (or brown) and belts with stripes for the uneven Kup numbers.
Austria: 10 Kups as well, but their 10th Kup is Yellow and their white belt is an additional Beginner level which is not part of their Kup-system.
The Swiss system is more similar to what some Korean Grandmasters are using. 8 Kups and 3 belt colors, Yellow for 8th and 7th, Blue for 6th to 3rd and Red for 2nd and 1st Kup.
Oh, France actually has additonal children Kup-ranks, so it's 15 Kups for children and 10 Kups for adults.
Getting further and obtaining a new belt can be very motivating for kids.
Between testings their shouldn't just be a wait time though, but also a minimum of training units. In Germany it's handed like this:
10th to 9th kup 3 months / 48 training units (45 min. each)
9th to 8th kup 3 months / 48 tu
8th to 7th kup 3 months / 48 tu
7th to 6th kup 3 months / 48 tu
6th to 5th kup 3 months / 48 tu
5th to 4th kup 4 months / 64 tu
4th to 3rd kup 4 months / 64 tu
3rd to 2nd kup 4 months / 64 tu
2nd to 1st kup 6 months / 96 tu
1st kup to 1st dan 1 year