Hello,
Please add this code to the Theme Settings > Custom CSS > Global:
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=text]::-webkit-input-placeholder { /* Chrome/Opera/Safari */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=text]::-moz-placeholder { /* Firefox 19+ */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=text]:-ms-input-placeholder { /* IE 10+ */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=text]:-moz-placeholder { /* Firefox 18- */
color: red;
font-weight:bold;
}
/**/
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=email]::-webkit-input-placeholder { /* Chrome/Opera/Safari */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=email]::-moz-placeholder { /* Firefox 19+ */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=email]:-ms-input-placeholder { /* IE 10+ */
color: red;
font-weight:bold;
}
.page-template-maintenance .mc4wp-form .mc4wp-form-fields input[type=email]:-moz-placeholder { /* Firefox 18- */
color: red;
font-weight:bold;
}
Replace “red” with the color as per your needs.
Best Regards