有無方法令舊的白皮錶帶去黃??

你可嘗試用膠擦或牙膏擦拭或用肥皂清洗, 但切忌使用強力溶劑,你也可試用較溫和的純酒精（99% ）去抹拭, 應可較易將污漬除去, 亦不會令表面模糊. 如果表帶變黃，可多用肥皂清洗，然後用乾布徹底抹淨即可。
希望幫到你!

你之前因未註明表帶的質料, 所以上面的回答可能未必完全適合你o 以下是本人針對你的補充而發出的個人見解:
所有錶帶, 不論皮帶或膠帶, 都有使用壽命的(受環境, 體汗侵蝕影響), 如經常佩帶, 很快報銷; 質地較好的, 壽命可長一點o 至於錶帶上的顏色, 由白變黃, 正是與日光+ 手汗所造成的結果, 無法還原呢o 提議更換一條全新錶帶, 如配不到原色, 嘗試與其他顏色配搭; 配置原廠錶帶比代用品貴很多, 而壽命亦不會延長太多, 不合付實際(經濟)原則o

You can try the above method, but it might not work.

Truth is, when a resin band is exposed openly, it degrades and ages in time. This changes the texture (and the colour) of the resin band such that it eventually becomes brittle and breaks easily.

A typical Casio resin band has a lifespan of about two years, given that the watch is used on daily basis. If the timepiece concerned is stored appropriately then the resin band may sustain a longer lifespan.

In your case, I suppose your G-shock is a very colourful one right? If this watch is past two years then it is very likely that the resin band may break at ANY time. Your best bet is to get a new resin band.