Both lighting and the colours in your tank will change the colours of your fish, and their mood too.
Light gravel will make the fish lighten, dark gravel will make them darker/more intense.
I had a common plec in a white bottom tank for a week, he went pale sandy brown, and the young killies in with him were pale and washed out. Chucked them in my other tank with black stones and the plec went black within a few hours, and the killies got darker and brighter. They adjust to their surroundings so if your fish is a noticably different colour in the log thats probably part of it.
Different types of light will bring out different colours in the fish - red, orange, yellow seem to show in any light, while the colours from the other types of colour cell (blue, green, gold foil, irridescence) are hugely affected by the colour levels in the light. They look best in sunlight, so if the sun comes in the windows of the room your tank is in, you can use a mirror to reflect it onto the tank to see if your fish are green in it.
The stripes on the angels are changed with their mood, mine are the same colour and i've watched them flick between almost white, then dark grey with 7 thick black stripes, to a gold and green colour with no stripes, to their normal 3-striped pattern, all within a few minutes. I haven't been able to figure out what they're saying with each colour change, but they show a more intense version of the normal stripe pattern when they are fed.
So - try sunlight, or a desk lamp with a normal lightbulb, and see how your fish look with that, then if its alot better try and find a new tube with the colour range to match. If not, look at adding more dark things to the tank, or accept that its their mood and they might darken once they've settled in more.