What is your dimension in the chart? Please use it it the expression.
The second expression return green color because it's the default color based on If condition logic when dimension not match Actual* or Forecast*
About coloring in combo chart:
+ Color by expression and measure: change color of all measure (bar, line, dot...), it means that for 1 dimension value, all measure will have the same color
+ If you want to have 1 color for bar, 1 color for line, 1 color for dot..., create these measures in master item, pick color for it, then use it in your combo chart, make sure that Color is set to Auto