[A1]  The original brick texture to which we'll add some changes.

[A2]  The simplest change to make is with the Hue/Saturation filter Just slight changes to the hue will give you a number of colour options. Here the hue has been shifted to a yellow/green that has been slightly desaturated to achieve a slate grey brick.

[A3]  Another technique is to invert the image then use the Hue/Saturation filter (set to around + or - 180)  to change the colours back to something more natural.

[A4]  Here the colours have been changed and the image rotated 180 degrees (remember that inverting the image turns the highlights to shadows and vice versa).

[B1]  For a painted wall texture, first invert and desaturate the original image.

[B2] Reduce the contrast using mid grey filled layer/object with the opacity reduced. Normal merge/paint mode.

[B3]  This gives you a bump map  to which you can apply bumped lighting effects

[B4] Next lighten the image using the levels dialogue   Finally, add a touch of yellow (or any colour you like) using the Hue Correction dialogue box

[C1] To give the bricks a little more depth and texture the 'bumped' image in [B3] can be copy > pasted and applied over the original image as a layer/object. The merge or paint mode is set to Hard Light and the opacity reduced to suit.

[D1] Here's another example of just changing the colour hue applied to this carpet texture. 

[D2]  Use the Hue/Saturation filter to change to blue. Here however, the colours don't look quite right.

[D3] To rectify this a touch more blue was added using the Hue Correction dialogue