Jazzy means bright and showy — or in the style of jazz. Two senses, and only one involves music.
The showy sense is the commoner one in British English, so a jazzy tie or a jazzy pattern is loud and colourful, and it carries a faint suggestion that it is a bit much. The musical sense means having the feel of jazz, and it is used loosely by people who are not musicians. The verb phrase jazz something up means to make it more lively or more colourful.
From jazz + -y.
Etymology from Wiktionary, CC BY-SA