There are many types of colour blocks, Regular, Pastel and Dark.
In-Game Descriptions
Note that items in bold vary depending on the color block.
Color Blocks In-Game Description
Blocks are available in a stunning array of colors!
Rarity: 9
To grow, plant an Orange Block Seed. (Or splice a Bricks Seed with a Poppy Seed)
Pastel Color Blocks In-Game Description
A paler shade of awesome.
Rarity: 7
To grow, plant a Pastel Yellow Block Seed. (Or splice a Magic Egg with a Yellow Block Seed)
Pastel Color Flower Blocks In-Game Description
A dasier shade of pastel.
Rarity: 17
To grow, plant a Pastel Blue Flower Block Seed. (Or splice a Magic Egg with a Pastel Blue Block Seed)
Dark Blocks In-Game Description
Dark blocks are available in a stunning array of colors!
Rarity: 26
To grow, plant an Dark Purple Block Seed. (Or splice a Grimstone Seed with a Purple Block Seed)