Following code works as expected.
<a class="twitter-timeline" href="https://twitter.com/kamicup" data-height="600" data-theme="light" data-link-color="#E81C4F">Tweets by @kamicup</a>
<script async src="http://platform.twitter.com/widgets.js" charset="utf-8"></script>
But, adding a line
<meta name="twitter:widgets:csp" content="on">
in the <head> tag cause failure, that data-link-color not to work.
Isn’t it a bug?