Well of course it does, a png doesn't have a colorkey flag.
However, with a png you can just set the alpha to 0 (this is always transparent, even if blending is off)
Here's a list of which palette corresponds to which text color:
enum text_colors
{
TEXTCOLOR_GRAY = 0,
TEXTCOLOR_BLUE = 2,
TEXTCOLOR_RED = 4,
TEXTCOLOR_PINK = 6,
TEXTCOLOR_GREEN = 8,
TEXTCOLOR_LIGHT_BLUE = 10,
TEXTCOLOR_YELLOW = 12,
TEXTCOLOR_WHITE = 14,
};