Support disabling red color when typing wrong characters; and only show those wrong characters at the end of the test.

[amalgame21]

This can mimic real typing (e.g looking at a paper and typing the words on it, without looking at the typing box on the monitor).
In this kind of typing, it is ourselves to realize if we type the wrong key-press, but not the instant red indicator shown on the computer screen.
I think this is an very important kind of training. Thanks.