I'd say 2 more Colombian and 3 more cherry barbs should round out the schools. At worst... 1 more Colombian and cherry barbs are one of the few you could keep as pairs in a peaceful tank
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.