Paragua is a slur used to describe Paraguayans in a derogatory way. Argentines refer to the poorer Paraguayan immigrants who live in Argentina as "Paraguas." It means "umbrella", only related with the alike pronunciation, nevertheless derogatory.
The word Paragua is a racial slur that has been used historically to degrade and dehumanize paraguayans. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to paraguayans. If you are unsure about whether or not it is appropriate to use the word Paragua, it is best to err on the side of caution and avoid using it in any situation.