//SETBKCOLOR, r, g, b
SETBKCOLOR sets the background color to be used for subsequent text output. The r, g, and b (red, green, blue) values have the same meaning as in the SETTEXTCOLOR directive (which see for a discussion of the RGB color system). The default background color is 255,255,255 (white), which is taken as transparent. Any other background color setting will cause a ribbon of background color to be written along with any text. For example, this would be necessary in order to print white on blue.
When one color is written on top of another, generally the effect is not additive. Rather, the last written foreground and background colors will prevail. The exception is when the background is 255,255,255 (white), this is taken as transparent and thus will not affect the underlying background color (allowing, for example, text to be written on top of an image.) If you wanted your overlay text to have its own white background, you should set the background color to 254,254,254, which is very nearly white but opaque rather than transparent.
