are these stretch marks?

This is on my upper, outer thigh and I have these on both of my thighs, I'm 16 and think they might be stretch marks due to puberty, but I've had them for a few years now an they're still the same colour, aren't stretch marks supposed to change colour after time? If they are stretch marks, why haven't they changed colour and what can I do to change the colour? 
Note: I haven't shaved my leg up there because I'm too lazy to ever shave above the knee 😂