Hi there,
I haven't ever seen this many colours used for Algebra tiles either! When you say that you have always done Algebra tiles as a tactile graphic with key, do you mean a texture key or an alphabetic key? I don't think that you would be able to maintain the size (and placement) of the tiles relevant to each other, if you placed the values inside the tooled shapes. The surrounding text refers to the colour, so I believe that you will need to indicate it in some manner. (It is difficult for me to visualize how the print looks in colour.) Are there several of these activities? Does the print always use the same colour for size and/or for negative vs positive values? Would it be possible to use your usual method and simply add a TN with the information you have stated in the last paragraph concerning the colour? Alternatively, if you used an alphabetic key, based on the colour name for each type of tile, it would give a clue to the reader and yet would only be 2 cells rather than the label that would need to be placed inside the shape. The explanation of the key symbol would have to include both the label and the colour. As long as the shapes remain proportionate, I believe that the concept could be understood.
This is the best answer I can give you, based on the information you have given me. You may also wish to check with the moderator of the Tactile Graphics section of the Forum.
Betty