Two-way ANOVA, what to do next? I used a 3x2 between-subject ANOVA to examine the effect of colour (three levels: colourless, light red, and dark red) and odour (odourless or not) on perceived sweetness. The results indicated significant main effects for colour and odour and also a significant interaction of these two factors. I don't know what to do next.


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*What post-hoc tests can I run to understand this interaction?

*How can I do it in SPSS?

 A: This comes up frequently on the site.  Odour has an effect, colour has an effect, and they interact.  Therefore, the degree of odour's effect varies across colour.  You know this now.  Look at the means and describe the amount of effects.
Let's say that you checked the effect of odour for light red and it was significant but it wasn't for colourless. What does that tell you? It actually doesn't tell you anything meaningful. It doesn't tell you there's a difference between those conditions because you didn't test that. And, you already knew there was a main effect of odour, did it suddenly go away? What does tell you there's a difference between the conditions is the interaction.  What happens if all of your simple effect tests are significant?  Does that help you interpret your interaction?  No.  You can't infer anything across your conditions from those simple effects.  
Please add a table of your 6 means to your question.  It is possible that you might need to test some kind of subset of the data but simple effects aren't going to get you meaningful info.  If you need anything, more than likely you'd need a 2x2 interaction or a direct test of the differences among effects.  But it's doubtful you even need that.
