Why should you used adjustment layer to change color in photoshop?
You don't need to use an adjustment layer, an adjustment layer
will effect any layers that are under that layer, and you may not
want to affect all layers, just one. An adjustment layer is good
for non-destructive editing, because it can be easily turned on or
off, or deleted without making any permanent changes to the pixels
of the lower layers. You can also mask out certain parts of the
adjustment layer by adding a layer mask so that it will only affect
a selected area, but remember, it will still affect all layers
under the first one, which may not be preferable if the layers have
any transparency.