Sorry, I meant the 500 series. I'm guessing the only difference is the applicator tip.yes, the 800 should be the same ink, they just have a larger tip. I just checked as well, the orange exists even in the 500 series, it's just not sold by amazon in France so I couldn't order it.
and there is not that much of a gradient, it's pretty much a bit darker just next to the base, maybe just insisting a bit more in that area would make it darker enough. If you don't want something as weathered as the original, i would recommend the aribrush tough as it will be pretty hard to get something nicelly uniform with the markers, especially if you want to try to have a bit of a darker base.