When your toddler shows interest in an object, for example a brightly colored flower outdoors or even a piece of fruit, emphasize the color of the object when talking to them. Instead of saying, "look at the pretty flower" or "would you like a banana," you would say, "look at the pretty purple flower" or "would you like some of this yellow banana." To help reinforce the colors, you could also print out color-specific coloring pages or a free file folder game to complete with her.
Introduce numbers and even counting to your toddler by including them in your daily routine. You can count pieces of clothing while sorting or folding with your toddler, count out pieces of mail as you sort through them and when you give him some food, you could say "here are your five carrots." There are many free toddler-appropriate printouts available on the Internet that you can sit with them and color so they begin to recognize numbers in their written form as well.
Shapes are all around and you must simply get your toddler to recognize this by naming the shapes of objects on a regular basis. If they are going to play with blocks, share the shape of the blocks with them as they play. If she is at the park playing there are many shapes you can potentially point out, such as a circle from a merry-go-round and rectangle from a slide. Another easy way to explore shapes with a toddler is to make some dough and form the shapes as you name them.
It may be a bit early for some toddlers to begin letter recognition, but there are free learning tools you can use at home to help them do so. Spread out some pudding, rice or flour onto a sheet pan and trace the letters into it as you say the name to him. You may also guide his finger through the substance to trace the letter. Create dough, as you did with the shapes, and form letters out of the dough for him to play with. There are also many free printouts available that are letter-specific, yet appealing to toddlers.