Hi Jeremiah,
You can set the text colour through CSS with .blocklyText
The attributes that are part of the font style in the theme (family, weight, and size) change the size of the text, which requires extra care from Blockly to make sure the blocks get rerendered correctly. The colour can just be changed through normal CSS.
To theme specific blocks, you can either use a different style for each block (by providing your own block definition) or, since you're already planning to use a custom renderer, you can make that choice in your rendering code.
Hope this helps, and sorry for the delay.
Rachel