Hello,
Thank you for your question.
To place the icon for mailchimp form as per our demo you need to go to admin panel -> Mailchimp -> Forms -> edit your base form and place the following code there
<p class="mailchimp-input-icon">
<label>Email address: </label>
<input type="email" name="EMAIL" placeholder="Your email address" required />
</p>
<p>
<input type="submit" value="Sign up" />
</p>
And here is a code snippet to change newsletter form placeholder color. Place it into the Custom CSS section in Theme Settings
.mc4wp-form .mc4wp-form-fields ::-webkit-input-placeholder {color:rgba(0,0,0,0.7)}
.mc4wp-form .mc4wp-form-fields ::-moz-placeholder {color:rgba(0,0,0,0.7)}/* Firefox 19+ */
.mc4wp-form .mc4wp-form-fields :-moz-placeholder {color:rgba(0,0,0,0.7)}/* Firefox 18- */
.mc4wp-form .mc4wp-form-fields :-ms-input-placeholder {color:rgba(0,0,0,0.7)}
Regards