Edit your SYSTEM.INI and update/add the following lines

[386enh]
;COMMENT The following 2 lines makes the screen black and the text white
MessageBackColor=0
MessageTextColor=7

Color codes to use(HEX) :

0 = black
1 = blue
2 = green
3 = cyan
4 = red
5 = magenta
6 = yellow/brown
7 = white
8 = gray
9 = bright blue
A = bright green
B = bright cyan
C = bright red
D = bright magenta
E = bright yellow
F = bright white