Starcki damsel (Chrysiptera starcki), easily. They are somewhat difficult to come across, and not the cheapest fish around (~$50-$80), but they are often found on divers den (most recently 12/27 for $90), and are a beautiful blue color with some yellow. Mine is often mistaken for a dwarf angel by less saavy reefers, very active, and cooler than my hippo tang imo. Springeri damsel (Chrysiptera springeri) is another option, easier to find but less personality and quite a bit darker (mine tends to blend into the rocks).
Another option that is potentially reef safe (depends on the specimen) is the pygmy cherub angelfish (Centropyge argi), very active fish as well.
I have a randalls assessor (ORA captive bred), tons of personality in a docile tank but is my most skittish fish, and it's basically black. Got him back when I had a 40g breeder, and even in the smaller tank this fish was not exciting.
You could also go with a biota mandarin, they eat prepared foods readily (reef nutrition ROE and arcti pods were my go-to), and are very cool and pretty, though they are somewhat cryptic (particularly at first), and start out very small. If you go this route I recommend rearing it in a tank with no aggressive tankmates (your current stock is fine) for at least 6-9 months, at which point it would be big enough to eat larger prepared foods, like maybe LRS nano frenzy or dry flake.
There are a handful of wrasses that are varying colors of blue, but most of them (including the ones I mention here) will outgrow <2ft of swimming space quite quickly. A Solon fairy wrasse (Cirrhilabrus solorensis) is mostly blue, with a red head, and quite peaceful. And a male leopard wrasse (Macropharyngodon meleagris) is a beautiful blue, but hard to find as a male and notoriously difficult to get to eat (they often arrive with damaged mouths and/or only eat live foods).
And of course the blue spot jawfish that
@JasonK84 showed (there was a thread for this last week -
https://reefloungeusaa.com/products/blue-spot-jawfish-pre-order which is easily the cheapest you'll find it by 2x or more).
Good luck, hope this gives you a few (too many?) choices!