<div class="g-recaptcha" data-sitekey="MY_SITE_KEY"><div>

<div class="rc-anchor rc-anchor-standard">
  ...
</div>

.rc-anchor-standard {
  background: #f9f9f9;
  border: 1px solid #d3d3d3;
  color: #000;
}

.rc-anchor .rc-anchor-standard {
  background: #ffffff !important
  border: 0px !important
  color: #ffffff !important
}