I don't know what "coloring" means. Perhaps this is the short-cut that I'm missing? Please explain.
I solved it both ways and had initially thought both worked tho' now I see the mistake in my "other" solution.
Coloring is basically a way to set placeholders meaning that certain cells will contain the same digit X. R1C1 is 3/6, so are R5C1 and R5C2. So if digit X is in R1C1, it'll be in R5C2 by eliminating itself from R5C1. This same digit will now eliminate itself from R1C5 (because its in R1C1) and R2C2 (because its in R5C2) and will therefore be in R2C3. Coloring's just a simple way of getting to this because you can color (or mark in some way like circling) the cells I mentioned instead of going 3/6 in your mind for each one.
Parallel Universe — April Sudoku Test — 19th-21st April70 posts • Page 3 of 3 • 123