The speedometer backlight on my 2007 Cobalt LT is out. The fuel and tach gauges are still backlit, just not the speedometer. I don't think it is a fuse problem, because it would be the whole cluster that would be dark, correct? Did some quick Googling on speedometer-specific light problems, with...
New Black Cat Custom (Black Cat Custom Automotive - Gauge Faces for all makes and models of cars and trucks - LED Lighting Upgrades) gauge installed, black gauge face with blue LED kit
***These are taken with the front protective clear plastic removed..... and with a phone