Sheaffer Skrip red ink is unusual. It's not the most intense red ink there is - in fact, it can look quite watery, especially if you use a thin nib - but the shading effect is quite good and it is about the only red ink that doesn't clog pens. In fact, some people use it in an old clogged-up pen just to help clean out the last of the crud. Apart from the colour, it's quite similar in properties to Skrip black which is what I use every day - no clogs, despite the pen only being flushed properly once or twice a year. The Skrip blue is a horrid greyish colour, though - you need to look elsewhere if you like blue ink.
