Besides the color difference, there won't be any negative effects to keeping variously colored N. davidi. I would very strongly recommend a filter. Shrimp are actually more sensitive to water quality than the average fish, and a filter will enormously improve water quality, as well as allowing you to do fewer water changes while keeping the water quality high. Shrimp are also sensitive to changes in conditions - including temperature. Because very small bodies of water (like a 2.5 gallon) are very prone to sudden changes that wouldn't make a good home for shrimp. The 30 gallon cube would be much more stable. Because of issues with water stability I wouldn't put any shrimp in less than a 5 gallon tank, even if they're bioload and size are small.
As far as temperature, N. davidi are able to handle a large temperature range so long as there aren't sudden shifts in temperature. Anywhere from 68 to 80 degrees should be alright.
Lots of live plants will help out compete algae growth. Making sure the light isn't on too long, you don't overfeed, and that you keep up on weekly water changes should also help with that. Cherry Shrimp don't particularly care for algae and will only pick at it. I had a large colony and they did virtually nothing for algae control. I recommend against starving Cherries in the hopes that they'll take to the algae. Cherries should be fed every other day, and they'll accept sinking fish pellets as well as food made specifically for Dwarf Shrimp. Instead you could get a different type of Shrimp like Amano Shrimp, whose natural diet is mostly algae. Amanos prefer algae and will eagerly eat lots of it, and 3-4 Amano should be able to keep a 30 gallon clean of algae. Amano are compatible with Dwarf Shrimp like Cherries as well as larger shrimp like Bamboo Shrimp.
Blue Bolt Shrimp are a type of Caridina Dwarf Shrimp. They're a bit more fragile than Neocaridini Shrimp like Cherries or others like Amano Shrimp. You might want to see how you do with more hardy species of shrimp before trying Blue Bolts. Like many Caridina Shrimp, Blue Bolts are much more particular about water parameters than Neocaridina Shrimp. Blue Bolts need temperatures in the low 70s (so you could need a heater for them), a pH of 6.0 to 6.5, and very soft water. They do not do well outside of that pH range long term. If you want to keep things relatively low maintenance, you might want to test your pH and not get Caridina shrimp if you'd have to adjust it.
Bamboo Shrimp are very high maintenance, so that's something to keep in mind. They'll need tanks established long enough to have their own microflora (around 6 months or so). They're current feeders, so will need a filter with a strong current to feed from with a feeding perch nearby, and they'll need to be fed at least a few times a day. They're built to be eating small bits of live food almost constantly. Speaking of live food, you'll need to either buy or culture live small invertebrates for them. Bamboo Shrimp do best in a tank with strong currents and lots of dissolved oxygen.
I'm not sure how high maintenance you want the planted aspect to be. But some good low maintenance plants that would do well with Shrimp are mosses of all types. Christmas Moss, Java Moss, Fissidens fontanus, you name it Shrimp will love it. Having lots of moss should also increase the survival rate of shrimplets. Anubias, Java Fern, Cryptocoryne, Subwassertang, Hygrophila and Ludwigia are other less demanding plants. For carpet plants, Marsilea and Sagittaria subulata are some of the less demanding varieties.
Lastly, Shrimp in general do poorly in new tanks that haven't been cycled yet. Cycling involves using a filter and an Ammonia source to grow beneficial bacteria that can break Ammonia down into less toxic forms that can be easily removed with water changes, and it takes about a month. If you've already added the shrimp to a new tank, you may need to do daily partial water changes of 25% or so daily until the beneficial bacteria that break down Ammonia into less harmful substances have had a chance to develop in your filter media. Otherwise some of those shrimp will probably die. Adding live plants can also help the tank cycle faster, as can adding Tetra Safestart to boost the beneficial bacteria population. If you know someone with an established tank, getting some filter media from then and putting it in your filter would also really help.
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