有咩方法可以o係買牛仔褲前知道佢甩唔甩色??

先講牛仔褲，牛仔褲係用 indigo 染料，甩色係 indigo 既特色，洗水洗得越多就越冇咁甩。
t-恤 甩唔甩色其實好 depends on 價錢，因為貴既 brand 都會對 crocking test ( 磨擦測試甩色既 test ) 要求越高，而且貴既染料甩色程度比平染料低。

你買既時候可以試下用一張 乾既 tissue 擦下件衫，但係咁試都唔代表濕左水唔甩 ga...

For Denim, you can try use your finger to rub the denim surface. Because the heat & mositure from yr hand/finger can simulate the wet condition to test the color fastness.