As I work in consoles every now and then, I run in that one problem:

Some text is written in Dark Blue over the Black background:

And if you can read that text, wow! (without selecting it first.

So... how could you change the color of that blue to make it readable? There is a way by sending some escape command to the console:

echo -e "\\e]R\\e]PC6495ed"

That command changes the color of the blue to a light blue (somewhat "cyan", although not light cyan.)

The "\\e]R" part is to reset the colors to the default. You may or may not want to do that...

The "\\e]PC6495ed" changes the blue color, or color C (12). The P stands for Palette. And the "6495ed" is the hexadecimal color. (the color as in HTML.) To change other colors, use the same sequence with a different color number and color code. For example, the background color can be set to white with: "\\e]P0ffffff" (watch out! now what you write will be gray on white if not white on white...)

Anyway, there is the result of that echo command:

Although it is still a bit difficult to read, I can see the letters this time!

Source: http://man7.org/linux/man-pages/man4/console_codes.4.html (search for Palette)