Recommendation

Here are some (the ones not linked are not on this site yet):

Green and Plot focused (no smut):

“Global Examination.”, The Hunters Gonna Lay Low, I Want to Be a Big Baddie

Yellow to green (smut possible not guaranteed):

Approximal Guide, Virtual Strangers, Mission: Save the Hunter, The Pizza Delivery Man and the Gold Palace, (Transmigrated as an Omega Who Snags His Alpha) (no age mentioned, gives the same feeling though), Dazzling Breath, Fate Mate, Late Bloomers

Yellow to Red (smut guaranteed):

(Kiss Me if You Can ) (I’m not 100% sure Chase it younger, but it feels like he is), From Your Almighty Cradle, Blossoms of the White Night, Kill My Love

Red to Black (100% smut):

“Placebo”, A Tree Without Roots, Bad Best

I think the top is younger in “the light i give you” i'm not rlly sure tho