To me shading and coloring relate to more than one note rendered at the same time by varying intensity of different notes in a chord, you achieve different shading and color. If you are talking of piano I can understand. Of course this is referring to a violin as vibrato and pizzicato are more related to strings but not with a keyboard. As I am not a violinist, can a passage with notes played in rapid succession have the same shading and colouring as that of a chord? Any music teacher here?
You're looking at "chords" in a piano, which context is pretty different from what the examiner is saying about violin performance.
If you're looking at chord per se, for example, a C chord comprising C, E, G, the shading is determined by the piano tuner and coloring by the timbre of the piano. Yes, even in an Equal Temperament kind of tuning standard, a good tuner with solid understanding of the theory can still influence the shading of the chord. A piano tuner who tunes in the sequence of 4ths and 5ths estimates the relative beats of the intervals, and
the progressive beats of the major 3rds will most certainly have the most impact on the shading of the chords. As for the coloring of the tone (not the chords), it depends on the "scale design" of the piano as well as the quality of the soundboard. Alaska spruce soundboard will almost certainly produce a different tone color from a Romanian spruce soundboard.
The pianist does not influence the shading of the chord. However, the pianist can choose the shading of the harmonization. For example, instead of a dominant 7th chord, one pianist may find the shading of a 9th chord more soothing, another may prefer a 11th chord. Most novices will stick to the basic cadence.
Yes, a passage with notes played in rapid succession, i.e. the melody per se, can have its own shading and coloring. In this context, the examiner is not referring to the shading and coloring of a chord. It's about how the player articulates the musicality of the song.