Proceedings published on JACoW are viewable in colour. Authors should remember, however, that some proceedings might be published in book form in black and white. Therefore, it's important to keep in mind that graphics must be clearly legible, readable, and comprehendable in black and white, as well as color.
Typically, graphics generated from programs such as tracking simulations--where the figure is made up from very large numbers of points or vectors--cause problems. When converting such graphics to PDF, the software is unable to compress the files, resulting in thousands of elements being slowly "drawn" on the screen.
There are two methods available to determine whether an image has this problem. Firstly, does the file take a very long time to print? Secondly, if the PostScript file is displayed (using Ghostview or GhostScript, for example) does it take a long time to display? The latter method can also be used to identify one figure from among several that is causing problems.
If you have access to the software used to produce the figure, check to see if there are parameters that can be adjusted to reduce the number of points that are plotted (averaging, downsampling, etc.).
Alternatively, reduce the figure to a bitmap image. Most bitmap images will display essentially the same as the original "plotted" figure while uing much less space. Some commonly available software packages that can handle this type of conversion are listed below. Figures can be imported to these packages and then reinserted into the document.