@CandiveOz I don't know how the colors were done for GF99 and SurfGF before, so I don't know why the change. But, we can talk about how they work now.
First, it seems a lot simpler to just say that SurfGF is now always the same color as GF99.
Second, bear in mind that Shearwater computers are generally designed primarily for people doing deco dives. Rec diving is a limited subset. For deco dives, the SurfGF is going to be above GFHi as soon as you get almost to NDL = 0 and then keep going up from there for the remainder of the diver's time on the bottom.
So, if SurfGF coloring behaved as you're suggesting, for deco dives, SurfGF would just be red pretty much all the time. Which is really not very helpful.
Other random thoughts:
Conceptually, GF99 would be a negative number when you're on-gassing. It only becomes a positive number when you are ascending and starting to off-gas (i.e. when the tissue tension in your leading compartment becomes higher than ambient pressure - and I'm being a bit imprecise here for the sake of simplicity). In practical terms, we never use negative values. And we only look at the value of the leading compartment. You could be on-gassing in one compartment while off-gassing in another. So, some compartments positive and some negative, at the same time.
When you are on the bottom and have been there long enough for your tissues to be saturated, your GF99 is 0. It doesn't go positive until you start to ascend.
So, this color-coding of GF99 will only have any effect when you are ascending.
If your GF99 is higher than GFHi, you have missed a mandatory deco stop. But, maybe you are doing that on purpose. E.g. perhaps you got in with GF30/70 but decided to ascend based on GF95/95 because something happened and you need to get out as quickly as possible. You could do so by monitoring GF99 and making sure it never goes above 95. When you get to your last stop, look at SurfGF and wait for it to drop below 95 to make your final ascent to the surface.
If you did that, your GF99 (and SurfGF) would be red almost the whole way up - which CAN be okay, if you're doing it on purpose.
If you are not doing it on purpose, the color-coding as defined is actually a bit too liberal, I think. Imagine that your GFLo is a lower number than your GFHi. E.g. you are using, for example, GF50/80 and not GF80/80. If your GF99 is higher than your GFHi, then it is way higher than your GFLo. It is way higher than the prescribed GF for every 10'/3m stop you were supposed to make on the way up to reaching your GFHi.
In other words, if you use a more traditional GF setting, by the time GF99 shows Yellow, you have skipped at least one mandatory deco stop and possibly more than one.
It might be more useful to make GF99 turn yellow if you have missed any deco stops. It would always be yellow when the current algorithm turns it yellow, but it would potentially turn yellow sooner.
