Custom Villager Summon Command
Solution 1:
Use the Damage: value. For example, this villager will buy oak, birch, spruce and jungle wood:
/summon Villager ~1 ~ ~ {Invulnerable:1,CustomName:Wood_Buyer,Profession:0,Career:1,Offers:{Recipes:[{buy:{id:planks,Count:64},sell:{id:gold_nugget,Count:1}},{buy:{id:planks,Count:64,Damage:1},sell:{id:gold_nugget,Count:1}},{buy:{id:planks,Count:64,Damage:2},sell:{id:gold_nugget,Count:1}},{buy:{id:planks,Count:64,Damage:3},sell:{id:gold_nugget,Count:1}}]}}