White, black and blue speckles

[Evit]

I've been busy doing a digital clean-up of another film lately, removing unwanted speckles from a home video product, and I noticed that, judging by colour alone, there are at least three types of speckles appearing throughout: black, white and blue speckles.
Anybody knows where they come from, at which stage of the film processing they are introduced, what do they tell us about the source used?

[PDB]

Is it a laserdisc? Sounds like laser rot.

[Evit]

No, it's "Uncle Buck" on Blu Ray. It shows countless speckles throughout the movie. Most are black (in different sizes), some white (small points, very small lines mostly or, more rarely, round large discoloration spots), some blu with white at the center. It's not the best release but it's the only one in existance, I figure they took a final print, an interpositive at best... but I was curious to know what they "mean".

From the review on Blu-ray.com

Slight print damage peppers the proceedings as well, as does even more noticeable ringing, intermittent flickering, minor telecine wobble and sudden spikes in the film's grainfield. Thankfully, detail remains impressive (for the most part), artifacting and banding are nowhere to be found, and other digital anomalies rarely creep out of the woodwork

[AntcuFaalb]

I don't know about the blue speckles, but white is usually damage to the emulsion on the (inter-)negative print and black is usually damage to the emulsion on the (inter-)positive print.

@PDB: Laser rot usually only shows us as multicolored speckles or black tape-like dropouts. White speckling is usually an "inclusion defect" which is not rot (since it's not progressive) due to it being debris caught between the plastic and aluminum layer.

[Evit]

This film has all three types of speckles. Leaving the blue ones aside, does it mean that they scanned a somewhat damaged interpositive (black speckles) which, in turn, already showed signs of emulsion damage (white dots) from the inter-negative?

[zoidberg]

Black or white specks can also be dirt, depending on it's place in the process chain it can be on the surface of the film stock or 'printed' into the image from the previous generation. Some of the round discolourations could be water damage.

[Evit]

As soon as I complete "screengrabbing" them all I'll post many examples so you can have fun recognizing them

[zoidberg]

What software are you using for the clean-up work Evit?

[Evit]

For micro-fixes like these I have to work on individual frames manually. I create little patches with Adobe Photoshop, these will be then imported into Premiere. Basically I hand-paint the difects out of the film, like they used to do in the 70s eheh. It's a stupid way to make things and takes forever but sometimes it's the only way.

[zoidberg]

That's cool, you must have tons of patience to do that!