The Text color depends on the color of the background:
Setting | Application | Display color (background)
A = 0
R = 255
G = 255
B = 255
=> Black text; 100% transparent background
A = 0
R = 0
G = 0
B = 0
=> White text; 100% transparent background
But with Kurviger 2.0.7 you have always a small line around the letters.
This design should make the text better readable.