Sample Time Colors
By selecting Format->Sample Time Colors, you can get Simulink to color code signal lines according to their sample times. Colors are only updated when the model is updated or simulated.
The most common colors are:
summary="This table gives the color, sample time pairings for Simulink's sample time colors. I couldn't get the MediaWiki markup to work"
|Red||Fastest Discrete Sample Time|
|Yellow||Hybrid/Mixed Sample Time|
For the rest of the colors and other information, see Enabling Sample Time Colors (the Mathworks website)
Note: Constant sample time will only be displayed if Inline Parameters is checked in the Advanced Tab of Simulation->Simulation Parameters. This is because constant blocks can have variables as their arguments.