Une robe à pois (with a dot pattern) - une robe tachetée (with an irregular pattern of color spots) - une robe tâchée, une robe avec des tâches (with stains on it)
spotty = pickelig spotty = fleckig
A spotty dog is "un chien tacheté / un chien avec des tâches" in French.
a blue dress in french is " une robe bleue".
The French word for dress (noun) is "une robe" (fem.). The verb "to dress" is "habiller".
"A white dress" in French would be "une robe blanche."
A cocktail dress is 'une robe de cocktail' in French.
habille-toi
A red dress is 'une robe rouge' in French. Robe is a feminine noun.
It depends on the context. If you are referring to a material pattern, you should use "à pois". If you are talking about a dog's fur, then use "tacheté". If you mean facial/body spots, the word is "boutonneux" (or "boutonneuse" for a female).
Course de cyclotourism
robe blanche
robe jaune