Why don't you have all the different color belts?
In 1886, Jigoro Kano, the founder of Judo, began the modern ranking system by requiring his students to wear a colored belt on their kimono to indicate their skill level. The idea came from public pools and gymnasiums in Japan, where lifeguards would use belts to grade swimmers so they knew who to keep a close eye on! In Okinawa and Japan, prior to this, there was no special outer designation of rank. In fact, the idea of "displaying" your presumed skill level in any fashion was considered to be in very bad taste - contrary to the principles of humility and etiquette that are the core of authentic budō.
Unfortunately, as karate and other martial arts spread throughout the world, the idea of "teaching karate as a business" took hold. Today, some commercial karate programs offer as many as 25 different colored belts, along with club patches and other various decorations for the belt and uniform. Children are offered "promotions" as often as every few weeks, with the excuse that it keeps them motivated to continue training.
The problem is that the idea of multiple, meaningless short term rewards is completely contrary to the serious study of a martial art!
With the SKA, moving from one belt color to another represents a clearly observable change in skill level. In a lot of commercial karate clubs, there's not a big difference between a "camouflage belt with one stripe" and a "camouflage belt with two stripes" other than the kid with two stripes has paid an extra $50 or so in testing fees and related charges.
Karate-dō is not Pokemon; you don't get prizes every time you play. Both school and adult life require the discipline to stay the course when working toward important long term goals; an authentic martial arts program teaches kids (and adults!) how to sustain their motivation in a way that builds character and produces lifelong benefits.  Shotokan karate-dō is about what changes inside of you, not what changes on your uniform.