ive just recieved my larger screen clocks.im going to change all the back light smds to blue ,the lcd screen has a orange card behind it so means even if i put blue leds in they will still be orange.does any one know if the card is available in othe colours or what its called

If you try to put blue LEDs behind an orange filter they won't show as orange - you won't get any light through!

If you try to put blue LEDs behind an orange filter they won't show as orange - you won't get any light through!

well i would just wouldnt be blue still show as orange

No, the orange filter will block the blue wavelength. You won't get any illumination at all.

No, the orange filter will block the blue wavelength. You won't get any illumination at all.

well on my old clocks that were orange ,i changed leds to blue and the blue lit up the screen but not blue

Well, if so it can only be because the passband of the filter overlaps the bandwidth of the LEDs a bit but it will still attenuate the light a lot.

"Every time you try to operate one of these weird black controls that are labelled in black on a black background, a little black light lights up black to let you know you've done it"

Well, if so it can only be because the passband of the filter overlaps the bandwidth of the LEDs a bit but it will still attenuate the light a lot.

"Every time you try to operate one of these weird black controls that are labelled in black on a black background, a little black light lights up black to let you know you've done it"

as you seem to know so much about this.do you know what the name is for the card that is on the back of the lcd screen.ive taken it of and its white on the back and orange on the front.when i took the card of you could see right the way through.just clear glass .

Sorry, no I don't. I just know a bit about optics. Hopefully one of the forum experts will be along shortly to help you out.

When you say 'clear glass' do you mean it's not coloured?

Sorry, no I don't. I just know a bit about optics. Hopefully one of the forum experts will be along shortly to help you out.

When you say 'clear glass' do you mean it's not coloured?

yeah its just clear glass

Ok, well in that case LEDs behind where it's clear should show through blue but if there are any orange areas with LEDs behind them they'll get blocked or dimmed.