Altering jpegs and gif in stylesheet

[sealift]

Hello, I'm new to html but have been put in charge of updating my companies website. I need to change the header and page marker on the site from blue to orange. After discovering the stylesheet I was able to see that these were actually .jpg and .gif files which is why I wasn't able to just insert the colour name (#FF7519) I wanted. I am not sure how to go about making these and do not seem to be using the correct terminology to find the answer through google. Can anybody assist? I'm using a Mac but do not have photoshop. Header file name: top_bg.jpg Page marker file name: button_on.gif I would like them exactly the same, just with a colour change. Thank you in advance. I apologise if this is posted in completely the wrong area.

[Ingolme]

There's a free alternative to photoshop "GIMP" which you can use to manipulate the images. However, for the gradient it's probably best you make a new image from scratch, just make a gradient and cut out a strip from it.Now that I look at it, the button_on.gif image can be substituted by setting the border-radius on the two right corners of the element and setting a background-color. If that's not an option, the paint bucket tool from GIMP would be all you needed to change the image.

[sealift]

Thanks Ingolme. I've had trouble downloading GIMP on previous tries, possibly because by Mac does have the latest operating system (?).But i'll try again to download it and see if i'm able to follow your steps. Thanks for your prompt reply!