Capture One helpfully offers you the ability to add both vertical and horizontal guides (rulers) to help you compose your product and still life shots. I use them on almost every shoot/image.
The default colour is orange, which is fine for a large number of photos but I like to change it to a more vibrant colour because I tend to see it better that way. So, to modify the colour press Command + , and head to the “Crop” tab. Then, down to “Guides” and “Colors” (just click on the rectangle box). Finally, head to the second tab “RGB Sliders” and paste the HEX # FF00FF in the little bottom right box. That will give you a Magenta colour, which is pretty vibrant. While you’re at it, you can change the colour of “Grid”.
That’s it. This is one of the first settings change I would recommend to anyone asking for Capture One Pro.
Do you use C1P? Lightroom?