Hi,
To change or remove the text about the privacy and terms you can edit your Acymailing language files in Configuration->Languages. Select your language and click on edit. A new window will open. In the toppabel you'll find all language constants. Find the constants you would like to change, copy the entire line and paste it in the bottom panel. There you can edit your translation string. If you want no text just remove the text betweene the quotes.
To change the tex color of the butto add the following css to your templates custom css file:
.acysubbuttons input.btn.btn-primary.button.subbutton {
color: #ffffff;
}
You can look up the selectors in you browses' dev-tools (right-click and inspect element).