Annatto is sometimes used as a food dye but not often as a spice and I have never used it.

Annatto tree with pods
Annatto flower and seed pods
Mature annatto seed pod
Annatto seeds
Annatto tree with pods
Annatto flower and seed pods
Mature annatto seed pod
Annatto seeds

Species:Bixa orellana.
South America.
Brazil is the main producer and exporter of annatto. The plant is also grown in the Philippines, having been introduced there by the Spanish.
Used Part:
Dark red seeds.
Bixaceae (achiote family).
Annatto has a weak, perfumed odour.
The botanical genus name bixa comes from a different Carib plant name, usually written bija or biché. The species name orellana refers to the Spanish conquistador Francisco de Orellana (1511-46). By confusion of the Spanish name with the French town of Orleans, the German name Orleanstrauch ("shrub of Orleans") emerged. Other names of this plant all stem from Indio tongues in Central and South America, e.g. urucul from Tupi-Guarani in the Amazon region and achiote from Nahuatl in Mexico.
The English common name "lipstick tree" refers to the cosmetic use of the plant. The common name "annatto" is derived from the Cariban Galibi name annoto, "annatto". The Malay jarak Belanda literally means "distant Holland".
Annatto is mostly used as a flavouring and food colouring in South America. In the Caribbean, the seeds are usually fried in animal or vegetable fat and the resulting dyed fat is then used to fry meat or vegetables to achieve a golden yellow to golden brown colour. Mexican cooks use annatto seeds and acetic preservatives mixed to achiote, a paste that dissolves in hot fat. This is easy to use and can be added to marinades and sauces to improve the colour.
The original Aztec drinking chocolate reputedly contained annatto seeds combined with vanilla, and using annatto to deepen the colour of chocolate was common in Europe until the 17th century. Today the spice is sometimes used to deepen the colour of butter or cheese but has little other culinary significance. The seeds may be used ground (often after soaking in hot water to soften them) or in form of annatto oil.
In Yucatan, meat is often marinated with a vibrantly yellow spice mixture of annatto, dried oregano, ground spices, garlic and the Yucatan chilli recado. The juice of bitter orange adds a distinct, acidic fruitiness. Recado-marinated meats are traditionally wrapped in banana leaves and baked in a hot stone pit. The technique can be applied to poultry and fish, but is most popular for suckling pig. Food prepared this way is generally referred to as pibil.
By Spanish influence, annatto also has made its way to South-East Asia. In the Philippines the ground seeds are added to soups and stews and meat is often marinated with annatto-coloured seasonings. In Vietnam, batters and coconut-based curries are often prepared with annatto oil. The Vietnamese version of Beijing duck, ga quay mat ong, uses annatto oil to colour the skin.
In China, annatto seeds are occasionally used in seasonings or in marinades for grilled or fried meat (usually pork), resulting in a bright orange meat surface. A chemically similar dye is contained in saffron which has a similar colour but which, with its incomparable fragrance, is much more than a colouring agent. Safflower, in contrast, does not have any taste and can therefore be used whenever colour is desired but no aroma is wanted. The other alternative, turmeric, has a strong earthy aroma and stains food bright yellow.