I would love to see the color selection of blocks in Alpha as numerous as Creative. My thought on this and how to apply it is below.
Dye system - 64 blocks +1 dye = 64 colored blocks.
Dye = Flowers (easy to spawn the colors with not as much work)
Block you use = Dirt. Its common and easy to get and currently all "creative" colors are based on dirt (so no extra work there)
Another thought for dye is killing monsters this would mean less work then creating multiple colored flowers I think.
For different colors like "aqua" or different shades of green use multiple types of flowers/dyes to get that color...can easily use the color chart to map the colors or just make your own combos to get each color.
This is a great game but I feel Alpha really suffers because of the lack of ability to make "perfect" buildings to your taste. This is the BIGGEST reason Minecraft is popular and sure Alpha is about "surviving" but its also about building your own world against the odds.