Hi Taffy. This is where BMP2000 comes in. Import your BMP texture into BMP2000 & set the transparency of the colour surrounding the person at 0. The palette number of the blue in this example is 187.
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Click the Transparency button & set the Transparency value of the appropriate colour to 0. Click Save Palette then Exit to return to the BMP2000 main screen. Finally save out as Extended Format BMP.
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It's a while since I've done this so I hope my instructions are correct.