Camera flashes are generally balanced for daylight equivalent color temperature. That means that the white balance used with flash expects a much bluer light than typical indoor lighting. If your flash is providing most of the light, that's perfect. But when it isn't, the color temperature of the ambient light is dominant.

That's what's causing the orange color here. If your camera lets you set the white balance manually (or even force it to auto), that will help that problem. It's difficult, though, especially when parts of the scene are lit more by the flash and other parts more by the ambient light, because then there is no single right answer for the whole image (see more on this at How do I take portrait photo with flash and good ambient light as background?). In some cases, as @heropup suggests, you can put a colored gel on the flash so that it comes out the same coloras the ambient — see Using Gels to Correct Light @ Strobist for a great article on the topic.

As for "flat", that's just what you get with direct, on camera flash. There aren't any shadows to give depth cues. This situation (award ceremony in a school gym?) never lends itself to great portraits, or even great documentary photography. My advice is to take the snapshot, and then if you want set up another shot layer in better lighting.