When you say you have 'digital filters' do you mean physical filters that you fit to your lens? In which case if they are fairly strong colours the red, green and yellow will certainly do the job - I've used filters and produced very similar results to using monochrome film with the same filters. Here they are – image captured in RGB and desaturated from filtered original -

To a certain degree tagging the word Digital onto things is a marketing gimmick - when CDs came out, for instance, they started to use the word digital on headphones - there's nothing digital about a filter or headphones in that context.

You should be able to look through your filters and see how certain colours seem relatively brighter or darker – reds will seem to leap out seen through the red filter and so on. If that is the case then the colours once recorded in RGB will, when converted to greyscale for instance, seem correspondingly altered (but obviously without the strong cast your camera has recorded.) It’s easier to judge the results once you know what you are looking for - many viewers looing at the examples above have struggled to see the differences but they are huge!

On page 30 of this week's AP Angela explains about using filters on a digital camera in more detail.