Some styles from your template are taking priority over the mod_sclogin's css files because the template has marked them as important. You will need to either edit your template or update the appropriate styles in the mod_sclogin CSS file for whichever theme you are using (located in /media/sourcecoast/themes/sclogin directory) to fix this.
Your template file that is doing this is flexo/css/presets/style1.css
Your Log In "button" style is at line 48
color: #579ad9 !important;
border-color: #cecece !important;
background-color: #ffffff !important;
The button:hover style is at line 67
color: #ffffff !important;
background-color: #579ad9 !important;
border-color: #579ad9 !important;
There may be more that need tweaking, but these are the ones you need to concentrate on first.
-Melissa
Login modal button colors
