Here is a more complete list of symbols, taken from this question.
Red: Macros
# = macro (think #define)
Brown: Core Data / Namespace
C = modeled class
M = modeled method
P = modeled property
N = C++ namespace
Orange: Aliased types
C̲ = Objective-C category
E = enum
T = typedef
Green: Variables
B = binding
ƒ = function
F = field
K = constant
L = local variable
O = IBOutlet
V = variable (can be ivar, global var, local var, etc.)
x = parameter (think f(x))
Blue: Methods
A = IBAction
M = method
P = property
Purple: Aggregate types
C = class (Objective-C or C++)
₠ = class extension
Pr = Objective-C protocol
S = struct
U = union
