You're not crazy. I live in my RV in the middle of nowhere in the Nevada desert, & my white Camco fresh water hose gets algae buildup inside all year round. In the summer I have to treat it with bleach down the hose for 15 minutes or so, then I have to spray the inlet screen with some pressure to get all the green slime off before running water through hose & hooking back up. If I don't, my water pressure will dribble down to nothing.
Now granted, algae is completely organic, & will cause absolutely no health issues...but that still don't mean I want it in my drinking water. I find it strange that of all the colors they chose for the drinking water, they chose the one that is most likely to photosynthesize & cause algae to form inside it. I mean that's just common sense that everyone knows.
I looked for suggestions, but finally decided to just replace it with a heavy duty black hose, which I also ran through a pvc pipe and buried for asthetics & insulation. Although I cannot look inside and see for sure, I'm pretty sure it fixed my problem, since I no longer need to flush with bleach, have no low water pressure anymore, & don't feel like I just drank out of a horse trough. Honestly, I'm guessing the genius who long ago determined that RV city water hookups hoses should be white did so because of how it looked, not considering its practicality. And the industry just continues to go with it because that's how it's always been.
My thought on that is if there's a better and cheaper way, that's what I'll do. To heck with the industry. Alot of their products are overpriced and unnecessary. In this case, they were just plain ignorant.