Window light is good if you are able to shoot during the day. In the evening you need to find other types of illumination.
A simple alternative is a lamp that you can position and angle. Place it to the side of the subject, replacing the window light. A white card reflector on the opposite side of the subject to the lamp will help you to control the level of detail in the shadows.
On the ball, © Matthew Palmer 2012, Canon EOS 5D Mark II
The colour of light changes according to its source, such as daylight. But even that varies; it is warmer (more red) at sunrise and sunset than in the middle of the day when it is cooler (more blue). The light on a cloudy day, or in the shade on a sunny day, is cooler still. These different colours are referred to as the colour temperature of the light source.
Similarly, artificial light sources have their own colour temperatures. Light from tungsten bulbs is orange whilst fluorescent tubes create a green light. Your eyes automatically adjust for these differences in colour temperature and the ‘AWB’ (Auto White Balance) on your camera normally adjusts for them successfully. You can also set the white balance from a series of presets on your camera; these include Day Light, Cloudy, Tungsten and Fluorescent.
When you are close to a colourful subject, Custom White Balance will give the most accurate images. Setting this varies a little between camera models, but essentially you move in to fill the frame with a sheet of white card or paper and take a shot. The camera uses this neutral image to set Custom White Balance. Check your User Guide for step-by-step details.
The advantage of the lamp is that it is much more versatile than a window. You can shine the light down on the subject, for example. Experiment with a range of positions to find pleasing results. Take your time and review each image carefully. There is no rush, the subject will not move or go away.