If you are trying to create the look you are seeing on packets of chips then the only way to achieve this is to have the labels professionally printed or use a printer that is specifically made for printing these types of labels. You won't be able to create that look with a standard desktop laser or inkjet printer. The labels on products you typical see in the grocery store or large retail establishments are normally pre-printed by a company that specializes label printing. Unfortunately, creating this type of label usually has some setup costs and the cost per label can be high if you don't require large quantities of labels.
Consolidated Label, a company that specializes in pre-printed custom labels, has a good video on to how to create the different foil label looks. https://www.consolidatedlabel.com/label-articles/custom-foil-labels-video/
The company who you select to print the labels would specify how they want you to send them the artwork and you would work with them to explain where you want the foil to show through.
Black works well on foil designs because it is opaque, but other colors don't necessarily show true because the foil changes the color if you don't put a white ink layer under the color areas to block out the foil. In most cases the label printing company is adding a layer of white ink under the color layer to make the colors brighter so the foil doesn't show through except where there is no ink. If you don't have that layer of white under the ink colors, the foil can make the colors seem faded. There is normally a layer added to the artwork file that shows the white layer of ink. The label company will normally help with the final changes to the artwork to make sure everything is correct.
If you still want to go the route of buying blank foil label sheets from OnlineLabels.com and printing your own labels using your desktop laser or inkjet printer then I recommend that you stick to printing 100% black only on the foils since black is the only color from your printer that is going to be opaque (where the foil won't show through it). In your design, you would want to reverse out the text or areas where you want the foil to show through. Anywhere where there is white or no color in your design there would be no printing since your desktop printer will not print white.
We are happy to send you samples of our blank foil labels for testing in your desktop printer if you would like to fill out our sample request form at https://www.onlinelabels.com/samples