Which lights are used as the DRLs does vary by model and model year, but the general function is mostly the same. Usually when the headlights are used as DRLs, they are illuminated at approximately half power, so will change intensity when switching modes.
When the light sensor detects a "daytime" condition, the DRLs are ON. The headlights, taillights, and side marker lamps are OFF. The instrumant panel lights are OFF, unless a progaramming change has been made by a dealer, in which case they are always ON. The radio and DIC displays are at maximum brightness.
When the light sensor detects a "nighttime" condition, the DRLs are OFF. The headlights, taillights, and side marker lamps are ON. The instrumant panel lights are ON. They and the radio and DIC displays are at a brightness level controlled by the panel dimmer switch. The maximum display brightness achievable is less than the "daytime" brightness.
The most consistent indication of day or night mode is the brightness of the DIC and radio displays. Twist the headlight control knob backwards, and, if the displays brighten, you were in night mode.