It's not selling because no one cares in Japan. I saw two types of advertising for Colours: Posters in Shibuya with speakers periodically playing samples from the album and the vans
(Linked because it's a big image).
However, when it comes to actually buying the album? Aye, good luck. Remember them photos from years ago when she released good albums and you'd see a massive display in Tower Records with all the copies selling out? There is nothing like that for Colours. I was in various record shops after the album came out, but before I left Japan and I didnt see a single copy for sale. That's not because it was sold out: It's because there wasn't even a section for it.
It's a terrible album and the (lack of) sales are justified.