Problem with the mobile version

My forum letters have become black and it's almost impossible to read because the background is dark.
I tried the "classic" and "modern" version and the forum behaved better on the classic version.. but still, the letters are black!
How can I turn them into white?
Thank you for your time.

I put the code in the CSS but nothing happened..
I must be doing something wrong..
In the instructions it says ID mpage-body
which I have no idea what it is..

Could you help me some more please?
I'm not that good when it comes to coding..

Code:

mpage-body {
   color:  YOUR COLOR;
}

or

Code:

mpage-body {
    color:  YOUR COLOR !important;
}

I tried both codes but they don't seem to work..
This is the code I tried.

Code:

 mpage-body {
          color:  #FFFFFF,
        }

The code is placed at the end of my CSS
What am I doing wrong?

try and add it at the top of your CSS files

The thing that changed was the title.. to white letters.. and not the comments which still remain black.
Any other ideas?
Thank you for your patience.

Anyone?