Having never written assemble (68K or otherwise), I knew I was out of my league ... but I persisted.
Line by line, I replaced the assembler code with straight C. I was able to scare up a Motorola 68K assembler book around Apple and I recall that there was one assembler code I could not find: it turned out that it was a 68020-specific operator (and since we're talking color picker I suppose an '020 could be assumed — some kind of bit-shift-with-mask or some such weirdness, FWIW).
(I guess each pixel of the "color wheel" was a rather complex calculation that someone had found benefitted from a straight assembler implementation — keep in mind you could slide the brightness/value slider and the wheel would redraw in real-time on those underpowered Macs.)
Apart from getting the assembler over to straight C so the PPC compiler could have something to compile I also had to move over the API. Color pickers were plug-ins and had a couple of calls that, again, I believe had a different signature on PPC.
To learn the API and test it I wrote an HTML color picker that was essentially an RGB picker that gave you hex values instead of 0-255. Further I did a crayon picker as sample code (I thought this was kind of "Mac-like", right?).
I was a bit surprised when the HTML and Crayon pickers shipped. Then, much later, when someone ending up "porting" the crayon picker to Mac OS X I suddenly had regrets at having not spent more time coming up with good names for the crayons. (There was a general pattern though: naming the grayscale colors after minerals for example.)
I was almost fired I think though when my crayon picker shipped and it got out that I had slipped some T.S. Eliot quotes into the resource names in the Color Picker modules. I was called "into the office" and told that I had fucked up.
It's true though, I had fucked up. I had let the "Easter egg" thing get to my head and wanted to leave my mark. I think they had to quickly rev the OS after stripping out the offending T.S. Eliot quotes.
(There may though have still be an Easter egg lying around where the crayons would wear down until Jan 1 when they would be restored to full size.)
(Also, that was the first time I almost got fired. The second time would come when I was on the Photos team some 15 or so years later.)