Basically, if you've got any shade of pink at all, you're in ketosis.
Dark pink may mean that you're dehydrated but also depends on the time of day you test. If you test first thing in the morning, then those lil sticks are likely to turn dark pink because your urine is more concentrated--it'll contain more ketones.
On the other hand, if you test after you've downed a couple of litres of water and had a few wees, they're more likely to be pale pink--or even not showing any ketones at all. But that doesn't necessarily mean you're not in ketosis, it probably means you've just flushed them all out, LOL.
The more ketones in your wee, the darker pink the stick will turn, it's as simple as that. But that doesn't mean that more ketones=better weight loss.
If you're sticking to the diet 100%, you'll almost certainly be in ketosis after the first two to three days.
And even if you aren't in ketosis (according to those pesky sticks) you'll still be losing weight, I promise.
Is this the point at which I confess I've never used them anyway (the only time I ever got tested was on my second visit to my CDC, just for her to confirm I was in ketosis)?
Happy CD-ing!