<svg width="50" height="50" xmlns="http://www.w3.org/2000/svg" xmlns:xlink= "http://www.w3.org/1999/xlink">
<rect id="blue-rectangle" width="10" height="10" fill="#0099cc"></rect>
<animate
xlink:href="#blue-rectangle"
attributeName="fill"
from="#00ffcc"
to="#0000cc"
dur="1s"
begin="0.25s"
repeatCount="indefinite"/>
</svg>