Figure 1
Compare 1 and 2 - there is just 1 difference i.e., outer shell
Compare 1 and 3 - there is just 1 difference i.e., shape
Compare 1 and 4 - there is just 1 difference i.e., color
Compare 1 and 5 - there just 1 difference i.e., size
No other figure has this property. Hence, figure 1 is odd one out.