To this date, in the civil fleet, black uniform, white shirts and gold shoulder straps have finally lost their sacred significance and ceased to be an attribute of a privileged position in society. So, the question is whether or not there is a need for a uniform? Ask at your crewing agency. Most companies do not need any uniform on board their vessels as long as it meets the requirements for personal protection equipment. Only about 20% of companies have the demand of wearing uniforms and some kind of insignia as a mandatory image attribute. But if this is the case, you will definitely inform about it. Otherwise, uniform is not needed. Predominantly, keeping to a more formal or informal style both by Master and the crew seems optional and depends on personal preferences unless the informal clothes are inappropriate to the occasion.
But, nevertheless, some seafarers, in particular deck officers and the Master himself opt for taking trousers, shirts, shoulder straps and blue sweaters with them to wear them on arrival at the port while the welcoming the authorities on board.
When the western blue sweaters were first introduced here in Russia, it looked cool and stylish. Even with no shoulder straps it hinted at belonging to a certain professional community. However, later the uniform sweater came into use everywhere and everyone started to wear it, including security guards from supermarkets, which made them and masters of vessels look very much alike.
Considering that any uniform is an established pattern of clothing set by a certain organization, wearing it without being prescribed to by your company is nothing but your own choice.