In a Dashboard, the sort is on the metric by default, not the dimension.
In order to apply the same color to all elements that have a common dimension across your boxes, you can change the sort in the Dashboards Manager so it's on the dimension instead. This can be done by editing the data set, clicking the gear icon to the right of the dimension, and selecting the sort you want to apply from the pop-under. You will need to do this for each box if you want the order, and thus the color scheme, to remain consistent.