藍紫色, also mistakenly known as 愛紫色 Ai Murasaki Iro, is one of Dir En Grey's earliest songs. It was never released in any form and only played live in 1997–98. Along with 刹那, 藍紫色 is one of the most famous demos by Dir En Grey.
According to internet sources, the song made its debut on 7 August 1997 on the first day of アルバム「MISSA」発売記念2Days at 大阪COWBOY WORLD. The official website confirms that the song was played on the tour final TOUR Deep [sink], Deep [gaze], Deep [agonize], Deep [-] Final More Deep [sympathy]～meet evil with evil～ on 2 November 1998. It is unknown when the song was played for the last time, but it was already gone by their early 2000-tours.
The song, which was also simply known as 新曲5 Shinkyoku 5 or New Song 5, begins with the words 白日の日には Hakujitsu no Hi ni wa, meaning On a day of bright sunshine, but the full lyrics are unknown. From what can be heard on a live recording, the song resembles a ballad, but with faster parts in-between.
You can listen to the aforementioned live recording of the song here.