Always remember the golden rule of cross stitch - keep your top stitches pointing the same way. This will make your finished piece look a lot neater.
Adding the last 1/4
Quite often you will need to add the other 1/4 of the cross in a second colour. You can either do this by adding the last 1/4 using the method above, or by adapting it slightly to add more dimension.
Option 1 - adding dimension
First, decide which of the two colours is meant to sit in front. Is one colour more background? Or is it hair that should sit in front of or behind the face?
Once you have decided, stitch the foreground 3/4 using the method described above. With the background colour, you are only going to stitch 1/4. It is easiest to bring your needle up from the empty corner and then down through the middle hole created by the previous colour (as with the green thread in images one and two). Where the 1/4 stitch is part of the bottom stitch (image two), make sure to push it under the top half of the stitch.
For this stitch, complete in the same method as detailed above, and shown in images three and four above.
The main difference for me is in the final presentation - option 1 adds less bulk to the square, particularly if there is also going to be a backstitch separating the colours. As always however, the choice is entirely up to you.
|The stitches on the right have been stitched using option 1|
The stitches on the left have been stitched using option 2.