As a concrete example, assuming the default palette, if you wanted to set animated pattern 28 to red and black alternating as fast as possible you could use The Listener to issue the following Lil snippet:
patterns[28]:35,47
To halve the speed you could double up each pattern index, e.g.:
patterns[28]:35,35,47,47
There are more examples of this sort of thing in All About Color.
Is that clear?