This is similar to imagine; it means to form a mental picture of something which may one day exist. It is often used to mean 'intend': We do not envisage making changes in the near future. This sounds pompous and also rather vague, implying that you have not really thought about the possibility of change. We do not intend to make changes is more definite, implying that you have made a conscious decision not to change.
The ‘Sun of May’ was added in 1818. The blue bands are a shade known as ‘celeste’, said to be the colour of the sky which inspired Argentine revolutionary Manuel Belgrano before battle. Effective date: 16 August 1985.