How do plants are green in colour and water blue in colour?

Green plants appear green due to the presence of pigment chlorophyll. Chlorophyll  absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum and reflects green light. Thus, plant appears green in color.

Similarly, when light strikes against water in large bodies, the water acts like the atmosphere and absorbs longer wavelengths and reflects blue. Also, the surface of the sea reflects the color of the sky, acting as tiny mirrors.

While, water in bottle and glass appear colorless, or takes the color of the bottle. Water to reflect blue light only in the larger water bodies, or at least 1 meter of depth.