I need a help to change color of some pictures

I bought a theme from template monster and i need to change the colors of the buttons till i reach the best colors matching togther , also to remove the background of the logo

First, backup your whole template. Get the images in photoshop or elements, and go to ENHANVE > ADJUST COLOR > ADJUST HUE \ SATURATION and mess with the first slider. The colors will shift through the full spectrum, from blue to red to orange, etc. Leave it where you want it, save the image in the same format that it was originally in. You’re good to rock.

Were there any instructions that came with the theme? Because it is a common task I wouldn’t be surprised if the theme folder had some PSD’s or if they allow colours to be changed via an interface or the CSS it is probably documented somewhere.

This is how I would recommend you do it.
A harder way of doing it would be to make a layer of white over the button then change the white to a color you want. After that just change the opacity to your liking.

you could probably get someone on fiverr to do some quick customizations like this for you.