Each recipe is orange until its yellow rank and grey from its grey rank. When the ranks differ, it turns green somewhere between the two; the client files give both ranks but not that point. Equal ranks go straight to grey.

Herbalism: Camping
RecipeMakesReagentsNeedsSkill-up
Incense Candle
Incense CandleYellow 20Grey 25
GreenhouseTaught by Blueprint: Greenhouse, requires 140
GreenhouseYellow 140Grey 145
Seed HybridizerTaught by Blueprint: Seed Hybridizer, requires 300
Seed HybridizerGrey 300
Gardening
No readable reagent record

From the Forever beta client files, build 1.60.1.70630: the SkillLine, SkillLineAbility, TradeSkillCategory, SpellReagents, SpellEffect, SpellTotems, SpellCastingRequirements and ItemEffect tables.