Thanks for the advice! I still feel like I haven't quite gotten the hang of the battle system yet. Is it true that you don't need to match the same ki orb colors with a character of the same color? For example:
Purple character is fighting a orange character and orange is strong against purple. What should I do ?
Option A) If I choose a bunch of purple ki orbs, then I'll recover some HP, increase the dokkan meter, and raise the purple character's ki circular meter which increases his attack power and may allow him to perform a super attack (if there's enough purple ki orbs to collect during his turn to attack). However, this comes at a cost of the orange character not being weak to purple, so the purple character's attack won't do that much damage.
Option B) Pick a different orb ki color instead. If I use a different color orb, then the purple character's circular ki meter won't usually increase that much because it's not purple, so purple character's attack power won't be that strong and they won't be able to likely perform a super attack.
note: What if the different orb ki color only has one available to use? Is it better to use it than to go with option A against that orange character regardless of whether that one ki orb color is blue, red or green ?
Orb colour only matters for healing and increasing Ki, it has no effect on the type of damage your character does. So if you have a purple character it'll always be a weak attack (and defence) versus an orange character.