This two coloured bracelet was made around the turn of the century. The clasp is highly decorative. The braded chains drape around the wrist like a cloth; a true sign of a quality piece.
Difference in colour in gold is attained when the alloy varies.
Pure gold is too soft and bendable to be made into wearable jewellery, so we alloy it, hence the 14k or 18k or sometimes even 24k. 18k for instance, or 750, stands for 750 parts of gold and 250 of something else. Depending on what we merge it with, the colour of gold changes. In this case gold was combined with silver and the yellow gold was mixed with silver and copper. 
Use lots of copper and the gold turns reddish, lots of silver and.. you guessed it.