Short of wearing a miners helmet, visual reference onstage in the dark was once just a daydream, and as we know, F may well be close to a 3rd string E, but on a slow atmospheric 'key of E' song intro on a gig, it can sound a million semi-tones away. 
 
Back in the early '70s, Alembic threw some revolutionary light on the subject by introducing LEDs along the top edge of the fretboards on their bass guitars. Some of the more eccentric artistes of the time utilised LEDs on the fingerboard face, too. Looked groovy, yeah, but it was seriously pricy, and usually available only as an option on top range instruments, which server to thwart widespread use. Much later, enter SimS Custom LED on the scene (as mentioned in What's New a few months back); Martin Sims developed the world's first retro-fit LED lighting system which allows fitting without removing the fret board, a major step forward given the natural reluctance of valuable and/or vintage bass owners to physically desecrate their instruments. The result is factory-finish quality and undetectable installation, all without changing the feel of the bass. 
 
Martin Sims, an experienced cabinet maker and engineer, is also a semi-pro musician who has personally experienced the problem of diverse lighting conditions during live performances. He realised the only solution was to make the elusive dot markers more visible. Seeking professional advice, he discovered LEDs could only be fitted to new guitars, invariably top of the range models. 
 
Preferring to keep the bass he was using, being happy with its feel and tonal qualities, rather than 'changing up', he thus sought an alternative. The result was revealed to the public at the London Music Show where Martin was also able to present green as an alternative to the standard red LEDs offered by other manufacturers. The choice has since been expanded to ultra-bright orange, hyper-bright red and the popular electric blue. 
 
Since its introduction, the fitting process (necessarily kept a closely-guarded secret by Martin) and electronic circuitry has been continually improved to the point where installation now utilises optic fibres just 1mm in diameter to carry light to the top edge markers. 
 
The front face LEDs have special lenses to disperse light more effectively and power consumption has been halved, thereby doubling the 9v battery life. Subsequently, the battery pack can last well over 60 hours and life expectancy of the LEDs should be well over 100,000 hours - far greater than the life expectancy of most bass players... 
 
More recently, SimS Custom LED has developed special tooling to be able to retro-fit the lights into carbon fibre instruments such as those from Status, Steinberger and Modulus Graphite, a task previously considered impossible due to the specialised nature of the materials used. 
 
The latest introduction is custom paint work, as illustrated here on the startling rip-fade example of the blue SSD N4. 

 
Stuart Spector Design N4, originally finished in black!

The   possibilities   for   painting   can   range   from   subtle   sunbursts   to   wild pearlescent fades with ripped graphicsor, alternatively, can incorporate names, logos or images. 
 
LED lights cost £12 each regardless of colour or position. Customers can specify anything from eight LEDs for the minimum number of dot markers up to an incredible 27 or more, as fitted to one customer's Steinberger. There's also an additional setting-up charge of £100 for each instrument which includes supplying a classy brass plaque to cover the power pack cavity, batteries, switches etc. Paint work starts from £80 for a straightforward colour change. The blue and white pearlescent rip-fade using two-pack automotive paints and high gloss lacquer would be closer to £450, but each order necessarily needs to be costed on an individual basis. 
 
Incidentally, SimS LED also offer general repair/maintenance work such as re-frets. Judging by the unimpeachable quality of the LED installations, your bass will be in good hands.