Red dye: smelt poppy, tulip, rose bush, or beetroot
Yellow dye: smelt dandelion or sunflower
Blue dye: smelt cornflower or lapis lazuli
White dye: smelt lily of the valley or bone meal
Black dye: smelt wither rose or ink sac
Green dye: smelt cactus
Brown dye: smelt cocoa beans
Light gray dye: combine gray dye with white dye or smelt azure bluet, oxeye daisy, or white tulip
Gray dye: combine black dye with white dye or smelt azure bluet, oxeye daisy, or white tulip
Orange dye: combine red dye with yellow dye or smelt orange tulip
Lime dye: combine green dye with white dye or smelt sea pickle
Light blue dye: combine blue dye with white dye or smelt blue orchid
Cyan dye: combine blue dye with green dye or smelt pitcher plant
Purple dye: combine red dye with blue dye
Magenta dye: combine purple dye with pink dye or combine red dye, blue dye, and white dye
Pink dye: combine red dye with white dye or smelt pink tulip or peony
Bone meal: craft from bone or use lily of the valley, white tulip, oxeye daisy, or azure bluet
Ink sac: obtain from squids
Glow ink sac: obtain from glow squids
Cocoa beans: obtain from jungle trees
Cactus: smelt cactus blocks into green dye
Beetroot: craft red dye from beetroot
Flowers: place in crafting grid or smelt in furnace depending on flower type
Lapis lazuli: mine lapis ore for blue dye
Rose bush: craft red dye from rose bush
Sunflower: craft yellow dye from sunflower