If my voice is too loud and green light turns to yellow light on the track header's volume field, how can I fix it? Change the recording level near piano roll or move volume slider in the track header?

On an already-recorded track, you adjust the level slider in the track header to lower the volume. If you want future recordings to be at a lower level, lower the level of the incoming audio with recording level slider in the Smart Controls panel (B) if available (if that slider is greyed out then you'll have to adjust the incoming audio level with the input level control on the interface itself or with the Mac input level control (System Preferences > Sound > Input) if there's no separate audio interface).

So recording level is still a volume? I mean, if I want my voice will be recorded more quietly, I lower the slider of recording level. If I want the voice sounds more loudly, I maximize a slider (volume) of a recording level. Right?

Yes, that's correct -- the Recording Level slider sets the volume of a signal before it's recorded (the level it'll be recorded at), the slider in the track header sets the volume of a signal after it's been recorded (in playback).

OK. Are there any common (for good quality) recording levels (75%, etc) for pop, rock and instrumental music? Do the levels of recording are different in different genres?

A good maximum recording level should be around -6 or so on the meter. In GarageBand the meters have no numerical level indication, so that'd probably be just before the green bar turns to yellow. You'd set the Recording Level so the loudest part of the audio to be recorded max out at that level. In playback the combined level of all tracks should show around the same level in the meter on the Master Track.

I don't understand the last sentence. How the combined level of all tracks look like? Do the all tracks' combined level is seen as a result of them by one level or one nunber under a master track? Or where can I see the combined level of all tracks? Do you have any video or screenshot about the last sentence?

In GarageBand, under the Tracks menu you can select "Show Master Track". All the other tracks are mixed together through that track -- the level you see there is the combined level of all tracks.

I don't know why the volume of a new track was set so low -- by default it should be at unity gain when you create the track. Logic lets you save custom default new track settings but AFAICT GB doesn't offer that option. Maybe you accidentally changed the default but if that capability is hidden in GB I don't know where it might be -- the Logic options do not appear in GB.