Why such a design for X?
There are 2 reasons for the choice.
1: X is the letter of enigma and mystery. at the same time it's symmetric and thus aesthetically pleasing. Also in the context of the product, X stands for exchange. Thus, the glyph becomes more relatable
2: The waves represent flexibility and the straight strike represents stability. Both of which are features client look for in any company.

Why the font selection?
The selected font gives an impression of formality and trust.

Color choice
Have used pastel green and blue colours for the glyph. Pastel colours are soft on the eyes and look great both in print and on screen.
Have used a shade of grey (instead of black) for the text. Grey gives an impression of formality and strength (think steel, or concrete)

A soft drop shadow around the glyph adds a subtle dimension to the overall look. It makes the glyph appear to pop out of the paper/screen, subconsciously making it more approachable for the viewer.