The boyband were the surprise addition of the television programme, which has seen fellow pop acts B*Witched, 5ive, Atomic Kitten, Honeyz, 911 and Liberty X reform over the past few weeks.
Best of Blue - which features their hits 'All Rise' and 'One Love' - has so far climbed up to number seven on the UK iTunes store's main sales chart.
Groups on The Big Reunion were unimpressed after it was announced Blue would also perform at their Hammersmith Apollo concert last month.
Although Blue haven't released an album in the UK since 2003's Guilty, they have been reunited since 2011's Eurovision Song Contest and released new album Roulette in Germany last month.
The Big Reunion airs on ITV2 on Thursdays at 9pm.
Watch the music video for Blue's 'All Rise' below: