For the specific issue in the screen grab you can add the following line to your skin and it should fix it.

#dashboard.own {
border-top: 15px solid #0c8a7d;
border-bottom: 15px solid #0c8a7d;
}

Alternatively, if you want a quick and wide sweeping fix, you could always use the wizard (skin > edit > use wizard) go to the color section, and change the header color to the one you want. This shouldn't actually change the header color from the dark grey you have now. Which I assume is because custom CSS ranks higher than any changes via wizard.