Shine a light.
On some of the machines at work if the digital dash does not illuminate correctly the numbers will show up with shining a flash light on them. You might try that on your gauges. If that works you can remove the gauge itself from the housing. Drill a small hole or holes and glue in small LED lights, then wire them in. If it works great, if not, you are stuck buying new gauges anyway.
Buckeye, Arizona(USA) 2011 Victory Cross Roads, Black police bag guards, black engine guards, black handle bars, Triumph Tiger mirrors, Triumph hand grips, set speedo/tach back 5" , adjustable timing wheel, Lloyzz Fuel Programmer III & air filter. Modified exhaust, made stock into 2 into 1. MRA windshield, Rotated front fender forward,relocated ignition switch, Bad Ace Fuel Tank Risers, Fat front tire.