Your BuyDisplay link shows an obsolete UTFT library (v2.79). UTFT is currently v2.83
It also shows you how to connect to a 3.3V Arduino Due or 3.3V 8051 chip.
You say you are using a library called TFT_ST7735
Google can find Bodmer's TFT_ST7735
Google can find Sumotoy's TFT_ST7735
Google can find MBED (not Arduino) TFT_ST7735
There might be others called TFT_ST7735.
If the regular library examples are showing the correct colours I would expect a BMP example from the same library to produce the same colours.
If you have got examples mixed up, it is easy enough to invert the colours e.g. tft.invertDisplay(1);
David.