Hang pictures of the colors labeled in Spanish throughout the room. Cut shapes out of colored paper. Glue a white label onto each color, then write the Spanish name onto the label. Laminate the shapes and hang them at a child's eye-level. Attach them with double-stick tape so you can easily remove the shapes and pass them around for children to see.
Introduce one new color each day. At the beginning of the day, pull down one of the color shapes. Ask children to name it in English, then say its name in Spanish. Ask children to repeat after you a few times. A few minutes later, ask them if they remember the name. Continue to ask them to name the color at several points throughout the day.
Review all the previous words each morning. After you introduce a new color, point to the colors you've already talked about and ask children to name them.
Use the Spanish names when you give directions for art projects. For instance, ask children to use "rojo crayons" to create pictures on the "blanco paper." Hold up these materials as you say the names to further reinforce their names.
Have children make crafts using the colors. Give instructions using the Spanish names without giving the translations. For instance, give children paper outlines of rainbows. Ask them to color in one line with a "verde" crayon but don't explain that this means green. If you've done enough repetition of the colors, children should be able to do this easily.
Help children make the connection between the Spanish and English words for colors by playing matching games. Make three sets of cards. One set should have pictures of the colors. Another set should have the color names written in English and the third should have the Spanish names. Spread out the cards face-up. Ask children to pair up the three cards that mean the same thing.