There is a good reason why these are all black and white. Most game engines allow you to manipulate the RGBA values of the textures in your buffer before being displayed.
For example, in my own OpenGL based engine I use the function glColor:
void glColor4i( GLint red,
As you can see, it takes 4 parameters. The first three, red, blue, green are values from 0 to 1 and combined can display any color on the visible scale. The last parameter, alpha, is a powerful tool to play with the visibility of the texture. That is, you can make the font semi-transparent, make the background transparent around the letter, or blend with the background.
Screenshot of an applied bitmap font with different colours and alpha channels in my project.
In my project I have used one of the tools you were referring to, namely to create an imagine of a font. There is a platherea of software and online tools available if you search for "ttf to bitmap".
Next I've written a class in C++ that allows me to display strings and position these anywhere on the screen. This includes the proper spacing for slimmer characters like"i", "l" and ".", as otherwise the words look stocky and unnatural. I also have a function call to the above OpenGL function and I often play with alpha values to make the font fade in or change the color to add emphasis. Here is an example of my current project, precisely applied a bitmap font and playing with the values.