Does the DT028BTFT (a-Si) and DT028CTFT (IPS, normally black) require different initialization code/commands? 

I tried replacing a Display from another manufacturer with the 28B and the 28B looked very similar (coloring was slightly blue).  But when I tried the 28C, the display colors were "inverted" where black and white were reversed (and colors were different). 

Note: I have not tried changing the initialization code to the code provided on your website (I will try this next)