Or better still. Click on the little compass on the lower right hand of the map and it will open up an editing menu. Click on the location where the yellow text is, then click edit text on the new edit window that opened up when you clicked the compass. Choose a color, save the map and your done. Then exit the editor.
Or if that is too complicated, go into the maps directory of your folder, open up the appropriate maps, and then edit the colors. The color of the text is after the /loc's. Since they are yellow, look for 255, 255, 0... To change them to black, replace the 255 with a 0 (zero).