Changing the text colour for App titles, subpages and usernames

I have changed the colour of the upper suite bar to be blue and I have moved the site title to be inside this suite bar.

But currently I need to change the username text colour to be white and I need to change the colour for the App titles from black to white.

I was able to change the title for the Site home page using the following code inside my custom CSS:-

#pageTitle {;  color:white}

But this will not have any effect on the App pages titles (library titles)or sub pages.

So my question is how I can:-

1. Change the color of the App page tittle ?.
2. Change the color of the usernames?

Thanks.

Currently my site looks follow:-

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I tried adding the following to my custom CSS :-

.s4-title h1 a, .s4-title h2, .s4-title h2 a{color:white !important;}

.s4-title h1 a, .s4-title h2, .s4-title h2 a{color:white !important;}