The 1881 1d Lilac 16 dots (S.G. 173/K8) is known with the PEARS' SOAP. underprint in outline letters in three colours, orange, mauve and blue.  Examples of all three are shown below:

K8l in Orange

K8l in Mauve

K8l in Blue

As a trial for the above a printing was also made with the words "One Penny" in two lines in black over the gum, as shown below:

 
K8n

This is very similar to the "Half Penny" underprint on the 1/2d Vermilion.

This stamp usually has a pinhole which, according to Stanley Gibbons, was introduced when the stamp was pinned prior to underprinting.  This seems rather unlikely to me as the pinhole in the above stamp is actually through the serif at the foot of the "n" of the "One" and appears to post date the underprinting.

Note.  The above stamp has a Stanley Gibbons Specialised catalogue number of K8 with the PEARS' SOAP. underprint being variety K8l and the One Penny underprint being K8n.