This is absolutely normal for about any internal combustion engine. There’s a lot of soot and other particles suspended in the oil. Every drop of old oil that remains during an oil change will immediately stain the new stuff black. One of the main jobs of engine oil is keeping the cylinder walls clean, so it will never stay golden for long.
Tl;dr: engine oil is supposed to do this, don’t worry.
I cut the piezoelectric speaker off of mine. It now doesn’t make any beeping noises, which is nice.