Function TextDrawBackgroundColor adjusts the text draw area background color (the outline/shadow - NOT the box. For box color, see TextDrawBoxColor).
If TextDrawSetOutline is used with size > 0, the outline color will match the color used in TextDrawBackgroundColor. Changing the value of color seems to alter the color used in TextDrawColor
If you want to change the background colour of a textdraw that is already shown, you don't have to recreate it. Simply use TextDrawShowForPlayer/TextDrawShowForAll after modifying the textdraw and the change will be visible.

(Text:text, color)
int text The ID of the textdraw to set the background color of
int color The color that the textdraw should be set to.

Return Values:
  • 1: The function was executed successfully.
  • 0: The function failed to execute. This means the textdraw specified does not exist.

new Text:MyTextdraw;
public OnGameModeInit()
    MyTextdraw= TextDrawCreate(320.0, 425.0, "This is an example textdraw");
    TextDrawUseBox(MyTextdraw, 1);
    TextDrawBackgroundColor(MyTextdraw, 0xFFFFFFFF); // Set the background color of MyTextdraw to white
    return 1;

Related Functions
The following functions may be useful, as they are related to this function in one way or another.