Provided that some bugs are forbidding your own CSS to take over .e.g your CSS is loaded still after corev4.css or you are using "Altenate Css" option in your site Settings (which reverts to previous point) you could add a CEWP with CSS styles along these lines, which however would be per page basis! Use any debuggers either from FireBug or IE8+ DEveloper Tools (F12) or Chrome (F12 also) to check the ORIGIN of your Style (.css file).
A more consistent solution would be to add these in your own CSS and load that in your master page, using somethig like this (in this example file is stored in the Site Collection Style Library but you could use _layouts too)
<SharePoint:CssRegistration name="<% $SPUrl:~sitecollection/Style Library/my/my.core.css %>" After="corev4.css" runat="server"/>
.ms-WPTitle
{
font-weight: bold;
font-family: tahoma,sans-serif;
color: #4c4c4c;
padding-left: 3px;
padding-right: 7px;
padding-top: 2px;
padding-bottom: 2px;
font-size: 10pt;
}
.ms-WPTitle A:visited
{
color: #4c4c4c;
text-decoration: none;
cursor: pointer;
}
.ms-WPTitle A:link
{
color: #4c4c4c;
text-decoration: none;
cursor: pointer;
}
.ms-WPTitle A:hover
{
color: #000000;
text-decoration: underline;
cursor: pointer;
}