The ends of the colorscale indicate whether values beyond the colorscale are shaded. For instance, on CAPE/CIN charts, CAPE is not shaded for values below 500 J/kg, so that end of the colorscale is flat. Values greater than 3750 J/kg are all shaded with the same color; ie., 3750-4000 J/kg will be the same as 4000-4250 J/kg.
On most thermal / thickness plots, the dashed lines follow a cyclical pattern of widths to make comparing two adjacent isolines easier. For instance, if the 5460dam line is thin and the interval is 60dam:
In general, a medium line is warmer than the adjacent thin line; a thick line is warmer than the adjacent medium line; and a thin line is warmer than the adjacent thick line. In the attached example, for instance, cooler air is to the northwest.
These buttons change both runtime and forecast offset in such a way that the valid time is maintained. On NAM products, for instance, B- moves the runtime back 6 hours while moving the forecast offset up 6 hours.