Hellow, how do I change the rollover (hover) font/text color in my navbar?

Here is the code:

CSS:

/* What it does: Hover styles for buttons */
.button-td,
.button-a {
transition: all 100ms ease-in;
}
.button-td:hover,
.button-a:hover {
background: #555555 !important;
border-color: #555555 !important;
}


HTML:

<tr>
<td width="20%" align="center" valign="top" bgcolor="#203b6f" style="text-align: center; padding-bottom: 15px;">
<center>
<table role="presentation" align="center" cellspacing="0" cellpadding="0" border="0" class="center-on-narrow" style="text-align: center;">
<tr>
<td width="110px" style="border-radius: 12px; text-align: center;" class="button-td">
<a href="http://www.cvent.com/events/2018-interface-seniors-housing-west/agenda-acb7447a9f594d7bad88835df6d3c986.aspx" target="_blank" style="background: #e2e3e4; border: 8px solid #e2e3e4; font-family: Helvetica, Arial, sans-serif; font-size: 15px; text-decoration: none; display: block; border-radius: 12px;" class="button-a">
<span style="color:#203b6f;" class="button-link">AGENDA</span></a>
</td>
<td>  </td>
<td width="110px" style="border-radius: 12px; text-align: center;" class="button-td">
<a href="http://www.cvent.com/events/2018-interface-seniors-housing-west/speakers-acb7447a9f594d7bad88835df6d3c986.aspx" target="_blank" style="background: #e2e3e4; border: 8px solid #e2e3e4; font-family: Helvetica, Arial, sans-serif; font-size: 15px; text-decoration: none; display: block; border-radius: 12px;" class="button-a">
<span style="color:#203b6f;" class="button-link">SPEAKERS</span></a>
</td>
<td>  </td>
<td width="110px" style="border-radius: 12px; text-align: center;" class="button-td">
<a href="http://www.cvent.com/events/2018-interface-seniors-housing-west/fees-acb7447a9f594d7bad88835df6d3c986.aspx" target="_blank" style="background: #e2e3e4; border: 8px solid #e2e3e4; font-family: Helvetica, Arial, sans-serif; font-size: 15px; text-decoration: none; display: block; border-radius: 12px;" class="button-a">
<span style="color:#203b6f;" class="button-link">REGISTER</span></a>
</td>
<td>  </td>
<td width="110px" style="border-radius: 12px; text-align: center;" class="button-td">
<a href="http://www.cvent.com/events/2018-interface-seniors-housing-west/custom-17-acb7447a9f594d7bad88835df6d3c986.aspx" target="_blank" style="background: #e2e3e4; border: 8px solid #e2e3e4; font-family: Helvetica, Arial, sans-serif; font-size: 15px; text-decoration: none; display: block; border-radius: 12px;" class="button-a">
<span style="color:#203b6f;" class="button-link">SPONSORS</span></a>
</td>
<td>  </td>
<td width="110px" style="border-radius: 12px; text-align: center;" class="button-td">
<a href="http://www.cvent.com/events/2018-interface-seniors-housing-west/travel-acb7447a9f594d7bad88835df6d3c986.aspx" target="_blank" style="background: #e2e3e4; border: 8px solid #e2e3e4; font-family: Helvetica, Arial, sans-serif; font-size: 15px; text-decoration: none; display: block; border-radius: 12px;" class="button-a">
<span style="color:#203b6f;" class="button-link">VENUE</span></a>
</td>
</tr>
</table>
</center>
</td>
</tr>

Any help is appreciated. Thank you!!!