If your natural color is medium brown, try light brown. This will yield a much better results than if you were to go for anything lighter. The red tones will less likely appear. In addition, ash tones will eliminate the warmth in your hair. Stay away from shades of gold as they will enhance the red and orange tint.
Permanent dyes are for lightening and camouflaging stubborn gray hair.
The will oxidize and fade in no time. Stick with semi-permanent dyes. They do a much better job darkening hair and with less chemicals than the permanent dyes, they turn out more naturally. Sometimes the results are sporadic. This happens more often to people whose hair has been constantly permed, colored, bleached, straightened or damaged.