There
could be several reasons for this -
More often than not paint chips are computer generated recreations of
colour, with every attempt to make them as close to the true colour as
possible.
The reflection of light can dramatically change colours, whether the
light be environmental or from light fittings, to the influence of floor
finishes and furnishings.
Colour changes over large areas, where more of the colour is
concentrated in the one space, as opposed to the effect of colour on a
50x30mm card. Colour can appear up to three times darker on a wall than on
a paint chip.
The simple solution is colour samplers. You can buy these in pots
ranging from 250-500ml which will allow you to cover up to one wall. As
opposed to painting onto the wall, consider painting a large sheet of
white cardboard or plasterboard, which will allow you to move it around a
room to take advantage of the effect of different light sources, shadowing
etc. Also watch the colour throughout the full day, colours can look
vastly different from day to night.
If you are happy with the tone of the colour, but would prefer a
lighter shade, this is possible, as all colours are mixed at 100% of that
colour, which means you can reduce the shade by a quarter, half etc. Some
colours may also be intensified, depending on whether they are at the
maximum for the base used ... this gets technical, so it's best to ask at
the time of mixing.
