I wanted to make similar but different blankets for my step-sister-in-law's twins, so used different patterns, but the same colours.
I worked out the colour distributions in an Excel spreadsheet, since the pattern calls for 3 colours, but I wanted to use the same colours in both blankets, and the other blanket called for 4 colours. See Excel screen clippings for the colour plan.
When the squares were finished, I crocheted them together, first in rows, then joining in columns - single line of crochet down the whole of each join. Finally, I edged the blanket in a simple shell pattern.