@trish_od - thanks for supplying a link to the site. Makes it so much easier to help. To replace the image in your theme, open the style.css file and find the following:
#navigation
{ clear: both;
float: left;
width: 930px;
background-image: url(images/header.gif);
height: 226px;
padding-right: 20px;
margin-top: 20px;
}
You can do one of 2 things:
1. create an image 930x226 pixels, call it header.gif and place (upload) it in the images folder of your theme.
2. upload an image and edit the css above to fit your new image. It's easiest if you keep the same width of the image. The hight is something you can play with.
To change the text colors/background colors:
Look through the style.css file for color: to edit text color and background-color: for background colors. Colors can be expressed in Hexadecimal values (#000000 is same as black and #FFFFFF is same as white etc.) or in RGB values ( rgb(255,0,0) or rgb(100%,0%,0%) is same red )
There are 17 valid predefined colour names. They are aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, orange, purple, red, silver, teal, white, and yellow. transparent is also a valid value.