in a sense these are but transliteration of エロゲ エロ本 to a degree, i think...

黄游（often stylized as 黄油 butter）is an erotic game, 黄曲 is a sometimes vaguely erotic song, 黄片 is video pornography, however 黄页 is just yellow pages even though you can argue it's also a media

i guess you would say 封面是黄色的 or something of that effect (黄封面书?), but yeah 黄书/黄色的书/黄本（子） probably always mean erotic material in a book form

i guess it's complicated, 红色 also has the connotation of communism, 黄色 means, for whatever reason, erotic, but 蓝色 is less clear what it should be, at least in the mainland (coastal). other less “正色” colors has less connotations, like i think “粉色建筑” just means a building that's pink

btw 绿色 instead of 绿色的 sounds like green as in bio-, organic and concepts related to that. 绿色建筑 means green (eco-) architecture, not a building that's green which 绿色的建筑 sounds more alike

“有绿色汽车” sounds rather weird, “有绿色的汽车” is better, “有辆绿色的车” is how i would say this. “绿茶” is kind of one word instead of an adjective-noun phrase. i think “绿” alone as an adjective implies some rhythm, “绿树” only makes sense next to “红花”

i did get tons of v6 traffic back in china though, troubleshoot?