Changing color of text box based on drop down selection

Hello,

I'm looking for a code that can be put into my adobe form that grays out other text boxes/sections based on a drop down selection.  Currently, I have 3 options at the beginning of the form (specialty) in a drop down menu, and would like the sections corresponding to the options not picked to gray out.  So, if someone picked option 1 from the drop down menu, the corresponding section for that choice in the form, with the fillable sections for options 2 and 3 graying out.  Is there a way to do this?