Robbin's comment: "Lizzy’s manner is so pleasing, entertaining, spirited, and charming that it is easily misinterpreted as admiration—at least to Darcy. I was wondering if she had the same effect on the Colonel. ;D"

Agree Lizzy is like this, and know this is what she values in society. She likes openness and sociability, like her own, reflected in Wickham and the Colonel, and this informs her preference for these men. She isn't swooning over "conseqence" like many others are, so in some ways, her own views oppose the oil on which society is running.

It's my own unpopular view that the Colonel does genuinely wish to join in some fashion/manner with Lizzy. He certainly seeks out her company singularly, listens to her music, talks of things with her that Lizzy has refused to discuss with Darcy. Lizzy did not want to discuss books with Darcy, because she thought their tastes would be too different at the Netherfield ball. This intimates, in doing these things with the Colonel, that there is some common ground. He engages with her match for match, and Darcy would not have been too excited about witnessing this. I am going by the Colonel's actions rather than his words, in forming an opinion, that he made all the initial overtures consistent with a view to companionship or something further, until the time came he had to leave.

However, there is no proof in the novel of the Colonel's "true" intentions, but I do get an overwhelming sense, that in the lines of order, Darcy is always first, or of more "consequence". The Colonel admits this himself, saying Darcy orders their stay and "the business" in Kent exactly as he pleases, (CH. 31) not at the Colonel's discretion. It's clear the Colonel does not have the clout that Darcy has. IMO, it's also clear that if the Colonel realised in one way or another, that Darcy meant to have Lizzy, he would have had to step aside. So if he knew, which cannot be confirmed from the text, but only guessed at, that Darcy meant to propose, it would have provided good motivation to say what he did say to Lizzy when they were in the park by themselves. Effectively, by his actions, he bowed out of the competition, and declared his real position. He didn't have to do this, and I always wonder why he so particularly did!;-D