Do you put only one color at at time out or a variety? How do you keep them from mixing the colors thereby ruining the stamp pads? I put out two colors, one for vowels, one for consonants to practice our sight words. We walked through the how-to and I placed an example of each word on the table plus had the vowels on one side with stamps and stamp pad and the consonants on the other side with stamps and stamp pad. I also limited the letters put out to those needed for the words we were working on. Any tips?