Find a way to do your custom CSS without !important
and things will go much smoother.
Often you can simply increase the selector specificity to properly override the theme.
Remove the important from this:
body, button, input, select, textarea { color: #d8d8d8 !important;}
and then this will work on the form:
input[type=email], input[type=email]:focus,
input[type=text], input[type=text]:focus,
input[type=url], input[type=url]:focus,
textarea, textarea:focus {
color: #000;
}
If you want to restrict that to the testimonial form, use this instead:
.strong-form input[type=email], .strong-form input[type=email]:focus,
.strong-form input[type=text], .strong-form input[type=text]:focus,
.strong-form input[type=url], .strong-form input[type=url]:focus,
.strong-form textarea, .strong-form textarea:focus {
color: #000;
}