Alternatively, you may write your text in a word processor that can make html code and paste the html code into the writing field. If the background is green then you are looking at the message preview, not the final message. If the background is white or gray then you need to turn off the color settings in your browser. If you have problems printing a message because of the colors then you may need to set the colors to black on white in your browser while printing. The messages look different in different browsers.
Some browsers support style sheets that allow a more detailed control of fonts, colors, etc.
The difference is only aesthetical and not important to the use of this board. You can navigate this message board without using a mouse. This only works in newer browsers. If your computer doesn't have an Alt key, then there may be another key for this purpose. A link without a highlighted letter can be accessed with the Tab key.