When you oil a pair of leather shoes, they usually turn a bit darker. The same thing happens with wax. A waxed garment has a slightly darker nuance than an unwaxed garment. For some colours, for example Pumpkin, the difference is more extreme, but on others it is hardly noticeable.
There are always fibres on the surface of a piece of fabric that have pulled themselves out of the threads. You can see this clearly on a pair of worn-out jeans, for example. The number of fibres "sticking up" from the fabric increases the longer you use the garment.
When you wax G-1000, the wax binds these fibres and the fabric looks darker. Since the wax is holding together the G-1000 fabric, it also becomes stronger and lasts longer.
Sometimes it is difficult to apply the wax evenly from the block of wax. This means that your garment will look striped after you have melted in the wax. You do not need to worry about this. Apply and melt a new layer of wax and the stripes will disappear.