Something needs to be said about utilizing and understanding the abilities of the gear you have and compensating your shooting style. You can try to force gear but it can only do what it was design for. It was not long ago shooters were shooting with ISO 800 and 1600 film without flash. I have seen and used ISO 400 without flash to get shots.
I have a D300 (very similar to iso noise with the 5100) and it simply does not have the same capability of a D700/D3/D3s/D4. You can get great shots, just not necessarily the same ones. As you push your camera's ISO you loose much detail and as you asked about, color as well.
1/250 is actually a very high shutter speed for indoors with the camera you have. 1/60th is probably more realistic what you are stuck with, although everyone would like that to be higher - the situation may not allow it. Above ISO 800-1600 you will loose quite a bit of detail so keep the auto iso to 1600 or lower. You didn't say what flash you are using, if it is the on-camera flash - just turn it off - it is useless over 10ft. SB-600/700/800/900 - 30-50ft is about all it can reach to good result. Many gyms ban flashes as it distracts players if you're gunning it from a distance. You may just be stuck without one.
To give myself a fighting chance, I shoot Spot metering, AF-C, and depending on the metering on the faces/subject, usually underexpose by -1. I find that cameras try to brighten the scene but lower the shutter speed too quickly - in post, bringing back 1-stop is fairly easy and faster shutter is a bonus. It's Not what I would like to do - but it is what the camera can handle coupled with what I know I can do easily in post.
Many times I will turn the Auto iso off for a while, set it at 400-640 and just focus on anticipating some pauses to get better shots. 90% of the time, that is what I end up using. Trying to "capture movement", I throw out 90% of those shots right off the top.
You can play with settings, but in reality learning to anticipate a shot at much lower isos is going to be key. Pick shots that your camera can handle - anticipate the brief pauses in the game. Don't worry about missing shots, if it was easy, everyone would be a sports shooter! 1 good shot in 20 is doing really good. As I don't shoot much sports and as it is just casual (for me), I would hope for 1 out of 100 to be really good.
grumble - just so you know Msmoto - my middle finger is extended at my screen in envy that you have your D4 at iso 10,000 and I'm stuck at 800. ;)
Thanks for your detailed feedback.
You may be right in that my expectations of ISO performance might outweigh actual iso performance. I guess these expectations were created by all the reviews stating how "great" the D7000/D5100 are with High ISO. Even DXO rated the iso capabilities pretty well.
I have no experience with high end FF camera's and thus no frame of reference. Maybe what I really need is a high ISO FF monster. Problem is, I don't have that kind of money. The most I could swing will be the D600 or D400 (dx).
If I'm interpreting your post correctly, you are suggesting that 1/640 is way to fast for "my camera" under these conditions and I should lower my SS somewhere between 250-320. Without flash, would that not cause motion blur?
I do have three flash units sb600, and two Sb28's that I use when I utilize the strobist technique of strobing across the court from the stands....but I'm still learning that and that should be another post. I would rather focus on using ambient lighting for this conversation.
I always shoot AF-C with 11 point dynamic and use the center sensor as my starting point.
I am shooting basketball tonight at a tournament and hope to try a few different tactics. This will be a new gym for me, so I have no idea what kind of lighting to expect.
I will post a few examples of each tactic.