This lets you pick the colors, widths and patterns of the lines that are used to log temperatures.
Temperature lines 1-4 are the colors and patterns of the first 4 logged temperatures, past that the colors start duplicating: line 5 uses the line 1 colors etc... The buttons on the right side show what the lines will look like.
Temperature Grid lets you choose the look of the horizontal lines indicating temperatures.
Last Temperature 1 lets you pick how the temperature logs from the last roast are displayed when you duplicate a roast.
Click the Name to choose a line color, click the display button to choose pattern and width.
When you are on the Choose a line style page, set the witdth and then press one of the line style buttons to choose that line style. Pressing "Back" leaves the line the way it was.