A borrowed chord becomes...diatonic?

I’ve been composing for about eight months, basically since I joined Hooktheory. This site cracked open what had always been a closed box.

Last week my singer sent me a little iPhone-recorded melody, which I set about to harmonize in Hookpad. It was in Bb minor harmonic, which we doesn’t seem available, but I could use a chromatic for the A natural.

It turned out that my favored opening chord choice was a borrowed diminished A, which came in with the rainbow ‘borrowed’ stripes. But when I chose the first inversion in order to have a C in the bass, the stripes were replaced by the pink that indicates the second.

I’d like to know why this happens, but I haven’t a clue what terms to look up. Well, sure, the bass note is the second, but how does inverting the very same notes result in a lowering of complexity?

Also, what key am I actually in now, Bb minor harmonic? Or has my opening chord made this ambiguous? The progression in in the attached image.

The chord colours correspond to the bass note rather than the root note. Since the bass note in Ao/C is diatonic, it is not striped (a double accidental that is enharmonically equivalent to another diatonic note will sometimes result in a striped chord, however it is not the case here and probably a bug anyway.).

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