I think the guy's a sergeant in the Singapore Armed Forces. Not a combat arm, judging from the colour of his beret.
As to your question, if you wear your jungle hat enough, and actually sweat in it rather then whip it out to strike manly poses infront of the mirror from time to time, it'll discolor slightly over time.
Shut up eggroll. I'm the Master Baiter! You watch yourself...
Without hurting anyone's feelings, why would you want to bleach your hat? Doesn't it get worn down enough just wearing it on a regular basis? Then again, I lose my PC's too much, so nothing looks worn for long. You can have my old PC from Benning once I find it in the desert! Damn it's gonna look like ****. Plenty bleached I hope.