They're getting there
There are two main ways of making 'white' LEDs.

The first is to combine multiple dies into one device, each emitting a different colour. So you would have a red, green and blue trio in a single enclosure, and by careful selection of the relative outputs of each, to the human eye the output is white light.

The other way is to use an ultraviolet, or at least deep blue, LED, and coat the inside of the enclosure with phosphors which will fluoresce and emit (usually) yellow light. Normally, the phosphor coating is applied sufficiently thinly as to allow some blue light through, so the blue-yellow mixture gives a whitish light.

With both types though, the colour rendering index is poor, due to the single spectral lines which are used, rather than the continuous spectrum of a tungsten filament lamp. This can be improved though by the use of more colours in a multiple-die device, or a range of phosphors in a fluorescent type.
( K2k6 has a proper job these days, Wed 14 Apr 2010, 12:45, 4 replies, latest was 16 years ago)

I think it was the phosphors approach that I was reading about a little while ago
thanks
( Vipros. clever got me this far, then tricky got me in, Wed 14 Apr 2010, 12:48, Reply)

Sensible post of the day winner

( Naked Ape call me Caitlyn, Wed 14 Apr 2010, 12:50, Reply)

Dat's interesting
We are looking at LEDs for the office, and have seen ones with differnt white colours.

I think the phosphor variant will be cheaper but the phosphor will probably wear over time, and change colour.
( Bartleby A dead man on vacation, Wed 14 Apr 2010, 12:52, Reply)

Phosphors have improved markedly
due to research into CRT technology (which unfortunately became obsolete around the same time as the technology reached a highly advanced stage!). So they're less likely to change over time as they were say 20 years ago.
( K2k6 has a proper job these days, Wed 14 Apr 2010, 12:56, Reply)

cheers

( Bartleby A dead man on vacation, Wed 14 Apr 2010, 12:58, Reply)

And LEDs are improving every day
For example:

this press release details a new product to be launched this autumn.
( K2k6 has a proper job these days, Wed 14 Apr 2010, 12:59, Reply)