getBackgroundColor black is not completely black in reality

Just made a datafield which checks if darkmode is active by something like this (can't post it, when adding as source code )...

var ColBack=getBackgroundColor();

if (ColBack==Gfx.COLOR_WHITE)
{    
     ColText=Gfx.COLOR_BLACK;    
     ColInfo=0xe00000;
}
else
{
      ColText=Gfx.COLOR_WHITE;   
      ColInfo=0xa00000;
}

dc.setColor(ColText,ColBack);
dc.clear();

When installing the datafield on my Edge 1050 I saw that standard datafields (timer, speed, etc.) aren't fully black but dark gray. So my datafield's black background doesn't match to the others. Does anyone know how to get the correct color tone for the dark background?

Bonus question: does anyone know if drawing functions (clear, drawText, drawRectangle, etc.) are faster when using a color instead of COLOR_TRANSPARENT? With other words, is dc.setColor(black,white); dc.drawText(0,0,font,"ABC",LeftAlign); faster than setColor(black,-1); dc.drawText(0,0,font,"ABC",LeftAlign);