Here are two different examples for you to work with:
First, this will attempt to change the color for ALL headings. It's pretty agressive and might change more things than you want:
h1,
h1 a,
h2,
h2 a,
h3,
h3 a,
h4,
h4 a,
h5,
h5 a,
h6,
h6 a {
color: palevioletred !important;
}
h1 a:hover,
h2 a:hover,
h3 a:hover,
h4 a:hover,
h5 a:hover,
h6 a:hover {
color: hotpink !important;
}
Or you could be more selective and try to change just post titles, page titles, and widget headings in the sidebar like this:
.posttitle h3,
.post h3 a,
#sidebar_right h4,
#sidebar_left h4 {
color: palevioletred !important;
}
.post h3 a:hover {
color: hotpink !important;
}
Try them out and see which one you like best. Adjust the color code as necessary.