What that does not do for them is sort out the colouring of the images, unless they scan a coloured image in the first place - but that limits the use. Often those stamps will be given away or thrown out to save space.
Others like to use line art to cut out and much is freely available but has the same issue.
So how best to add colour? There are several options.
The first is to simply add colour in the cutting software but this often will not produce the effect wanted, blocks of solid colour or simple gradients are the most likely options.
Hand colouring is a great option if you are artistic and have the supplies. The cake on the card here was hand painted on a blank shape. All you really need are some water brushes (convenient hollow handled), Pentel make some good ones, some kitchen towel and a small palette of watercolours, or some water-soluble crayons. The secret to getting that soft edge is to start by brushing the area with a damp brush. Then, pick up some watercolour on the tip and work from the outside to inside. Wipe excess water and paint off on kitchen towel. The paint will bleed into wet areas, so work on one section at a time, say the top of the cup cake and then the wrapper.
The last option is to use a piece of software that has brush effects in it. Software for cutting is Vector based, SVG, vector PDF (think dot to dot). Raster (JPEG,PNG etc) based software is also sort of dot based but in a different way, dots of colour forming an image by clustering together. This is the sort that realistic brush effects use.
There are many desktop graphics suites that will work in this way, some for Mac and some for Windows. However, for small embellishment files, I do like to doodle around with my iPad. I can use my fingers or a stylus to 'paint' directly on my screen.
One such is an app for the iPad called Touch Image Manipulator, available from the App Store for £0.79. Yes, that's right, under a UK pound. Here's a short video I made, that shows you how it works.
EDIT there was a tech problem, here is the new video!
Basically you can import your image from your photos. Then you can use fancy brushes to colour in the design. The great bit with this particular one is that it has masking ability that is soooo easy to use that even novices can colour with panache. You can choose if you want, to have a printers bleed, just to make sure there are no white areas, just 'grow' or 'shrink' the mask to get it where you want it.
You can paint with your finger or stylus without worrying about accuracy.
You can get that soft airbrushed look quickly and easily. One of the advantages of using this method is that you can re size your image at any time, and print, rather than get your paints out for every design. I expect there are android apps that do the same.
TIM allows you to import an image from your photo album or create one from scratch. All sorts of paint effects can be added. Just play until you see something you like! Once you have finished painting it, it is saved as a raster image, so if you started with an SVG(vector) line image, the two put together in cutting software will make up a print and cut. If you rely solely on a raster, you will have to trace it as normal in SCAL or whatever to get the cut lines. Generally, I email the images to myself and then save them in a dedicated folder. It means I know where to find them later!
Believe me, you can have hours of fun with this, your stamped images will never look boring!