Some kids can start recognizing and learning colors as early as age 18 months.
So it's a good idea to start teaching your kids colors by age 18 months and you can do so sooner than that but the child may not be able to recognize the colors earlier than 18 months of age.
But it's a good way to get them started on the colors.
By age 2 the child can recognize more colors and by age 3 they should be able to name a few colors and by 5 and 6 they should be able to fully recognize colors and be able to say what colors are which.
All kids are different and learn at different ages and can take longer than others to learn.
It's good to prepare children as early as possible to learn colors and other things which helps prepare them for preschool and kindergarten.
Your child will learn more colors and learn to name them more easily in Kindergarten and Preschool but helping them learn at home helps them know more about them when they enter kindergarten or preschool.