My relative and i buy the bijou at the same times but I had burn in 80hr while he too busy with his work, and just burn in arround 24 hr only. He and i are really curious how far the performance than burn in longer time vs less time. I told him to try himself to figure out because only the ear can tell u the true. what the forumer give might be fake . This is what i get the quality after the burn in.
Here is the review on 24hr burn in bijou vs 80hr burn in bijou
I just use the Sony k880i hp as a player and use the convertor to play the songs. Various of songs had been listen, and most of them is Jay chou and Jolin songs. after all, the comparison of both bijou is very obvious. Both of us agree with the final results. The 24hr burn in bijou seems less details, less punchy, soundstage a bit blur..the 80hr bijou just like put the ward in the bijou and all the details become clear and all the hidden background become visible.

Besides that, i found out that the foam is very important..Try take it out that original foam and listen, u will notice that the sound is leaking very serious.. but after put in the foam, all songs concentrate into your ear. Last time i didnt even play around with the foam. I just use the original foam that attach on the iem. After play around with the foam, i experience different sounds as well.. Therefore, make sure the foam u use is comfortable and suitable for u.

The foam that given
smallest with 2 layer  - inside the small plastic bag
small - at the IEM there..
mid - at the plastic holder there
big - at the plastic holder there
big with 2 layer - inside the small plastic bag

After testing the foam, i found out that I suit the mid one foam and my relative also wear the same mid foam.
How strong the bass, i think that
x3i > bijou (3) > xbi

Hope can try bijou (4), and maybe it bass is same as the x3i

About the color of the bijou, i think they use color to label the class of the bijou
Ruby - 1
pink - 2
gunmetal - 3
black - 4