Pre Modern Andalites developed this mode of locomotion (leaping into the air using all four legs, landing back on all for legs, leaping back into the air while moving forward) for many reasons. To signal that they are the most physically fit, the most attractive, to gaina better sight advantage while fleeing or to deter/distract predators while moving in a herd.
Now a days an andalite may pronk out of sheer enjoyment or as an expression of overflowing energy/enjoyment.
Double Dew claws (note, I saw another artist do this first a while back, artist who originally started doing this please step foreward)
Since the theme on the andalite homeworld is “extra” digits it makes sense to apply that to their lil andalite toes. A hoof is basically an evolved hand that has whittled down to the most essential support. While earth animals have evolved from five toed and have two dew claws it makes sense that andalites would have more considering they have 7 digits on each hand.
These particular markings are called Stockings. I also put a blaze on the face.
When animals become domesticated the desirable traits are linked to different markings, even when no effort has been made to breed for color or markings.
Human beings have been self domesticating as social civilized creatures must in order to survive, the traits of passiveness, intelligence etc have been selected for. (in return, smaller jaws, bigger foreheads..)
Headcanon: When andalites are described as blue and tan, the tan parts are markings, much like domestic horse markings. There are andalites with stockings and blazes and socks and spots aka ADORABLE.