Hi nylarosie. You could use any image editing application. If you’re using Windows you could use the Windows Paint application. Open the image file in Paint, select your primary (Color 1) color, click the paint bucket icon in Tools, then click on the image (the cursor will change to the paint bucket when it’s in the image). It should change the image color. Save.
Then you need to place that file in your child theme. I’d recommend the same path so you know where it originated in the parent theme:
/childtheme/assets/front/img/sidebar/file.png
Then you need to find the related css in the theme main.css file. Depending on which page layout you’re using, copy those lines to your child theme style.css. It would look like this for the left sidebar in a 3-column content middle (3cm) layout:
.col-3cm .main-inner { background: url(../img/sidebar/s-left.png) repeat-y left 0; padding-left: 340px; padding-right: 260px; }
Then you need to modify the url to look at the correct path based on where the modified files are located in your child theme. Based on the above path it would be this:
.col-3cm .main-inner { background: url(assets/front/img/sidebar/s-left.png) repeat-y left 0; padding-left: 340px; padding-right: 260px; }