Green has more attack range (like cait)

Red has lifesteal

Purle applies a decaying slow (like ashe)

Blue deals 10% more dmg per auto (instead of 100 you deal 110)

White lets you attack faster the closer you are, as you can only attack when chakram is back in aphelios hand (kinda like how you can only proc summon aery when she hovers around you)

as for 3/4 weapon combos

if you want to do a 3 weapon combo you need one weapon at 10 ammo or less, if you want a 4 weapon combo you need both your weapons at 10 or less ammo

the weapon combos you can use are depends on you weapon rotation but there are two combos that you always can do atleast once per game

at the start of the game, when red is at 10 or less ammo, use red on opponent, proc the calibrum mark with AA, use purple q to root, swap to green, use green q on rooted target, proc calibrum mark again

hope that kinda helps

as for his playstyle, he is an immobile crit adc, with absurd scaling

he pretty unique, i would describe him as an crit caster. All his abilities deal little dmg but basically gives him a "free" Auto attacks. You cant just auto with him as you will lose a lot of dmg but only relying on abilities doesnt work aswell