Product Version = NetBeans IDE 7.2 (Build 201207171143)
Operating System = Windows 7 version 6.1 running on amd64
Java; VM; Vendor = 1.6.0_25
Runtime = Java HotSpot(TM) 64-Bit Server VM 20.0-b11
gcc 4.5.3

The following (annotated) messages:

RED:  SlipHeader.h: In member function ‘virtual std::string slip::SlipHeader::toString()’:
BLUE: In file included from SlipSublist.cpp:12:0:
BLUE: SlipHeader.h:220:76: error: passing ‘const slip::SlipHeaderOp’ as ‘this’ argument of ‘virtual std::string slip::SlipHeaderOp::toString(slip::SlipCell&)’ discards qualifiers
RED:  SlipSublist.h: In member function ‘virtual std::string slip::SlipSublist::toString()’:
RED:  SlipSublist.h:143:78: error: passing ‘const slip::SlipSublistOp’ as ‘this’ argument of ‘virtual std::string slip::SlipSublistOp::toString(slip::SlipCell&)’ discards qualifiersnbproject/Makefile-Debug.mk:90: recipe for target `build/Debug/Cygwin_4.x-Windows/SlipSublist.o' failed

Should be:

RED:   SlipHeader.h: In member function ‘virtual std::string slip::SlipHeader::toString()’:
BLUE:  In file included from SlipSublist.cpp:12:0:
BLUE:  SlipHeader.h:220:76: error: passing ‘const slip::SlipHeaderOp’ as ‘this’ argument of ‘virtual std::string slip::SlipHeaderOp::toString(slip::SlipCell&)’ discards qualifiers
BLUE:   SlipSublist.h: In member function ‘virtual std::string slip::SlipSublist::toString()’:
BLUE:  SlipSublist.h:143:78: error: passing ‘const slip::SlipSublistOp’ as ‘this’ argument of ‘virtual std::string slip::SlipSublistOp::toString(slip::SlipCell&)’ discards qualifiers
GREY: nbproject/Makefile-Debug.mk:90: recipe for target `build/Debug/Cygwin_4.x-Windows/SlipSublist.o' failed

Where the following is of note:
[1] The 2nd RED should be a BLUE if it refers to or elaborates on the first (RED) error. I have listed it as BLUEin the 'Should be'  but this may be wrong.
[2] The GREY line is erroneously concatenated to the error line.
[3] A means should be provided to better display compiler output:
     a. Perhaps multiple lines with indentation.