Dear student!
We are not able to provide answer of all of your questions because we have to answer questions of large number of students in very limited time.
Here I am providing you the answer of you the most important of the three.
Colour of coordination compounds is due to their metal ion. The metal ions absorbs certain wavelength of light and reflects the opposite color.
Actually, when ligands attach to a transition metal to form a coordination complex, electrons in the d orbital split into high energy and low energy orbitals. The difference in energy of the two levels is referred to as ∆, and when the transition of electron occurs certain wavelengths are absorbed, subtractive color mixing takes place and the coordination complex solution becomescolored.
The complementary colors are the colors which mix together to give white light so the colors directly opposite each other on the color wheel are said to be complementary colors. For example, blue and yellow are complementary colors; red and cyan are complementary; and so are green and magenta.
So, in case of colored compounds for ex: Copper(II) sulphate solution is pale blue (cyan) in color because it absorbs light in the red region of the spectrum. Cyan is the complementary color of red and so, we can assume the color of compounds.