Here's the color codes copied from the AMHA studbook.
ABA APPALOOSA BAY
ABK APPALOOSA BLACK
ABR APPALOOSA BROWN
ABS APPALOOSA BUCKSKIN
ACS APPALOOSA CHESTNUT
ADN APPALOOSA DUN
AGL APPALOOSA GRULLO
AGR APPALOOSA GREY
ABN APPALOOSA ROAN BLUE
APA APPALOOSA PALOMINO
ARB APPALOOSA ROAN BAY
ANR APPALOOSA ROAN RED
ASR APPALOOSA SORREL
ASD APPALOOSA SILVER DAPPLE
AWT APPALOOSA WHITE
DBA DAPPLE BAY
DBR DAPPLE BROWN
DBS DAPPLE BUCKSKIN
DCS DAPPLE CHESTNUT
DDN DAPPLE DUN
DGR DAPPLE GREY
DPA DAPPLE PALOMINO
DSL DAPPLE SILVER
LBA PINTALOOSA BAY
LBK PINTALOOSA BLACK
LBF PINTALOOSA BROWN
LBS PINTALOOSA BUCKSKIN
LCS PINTALOOSA CHESTNUT
LDN PINTALOOSA DUN
LGL PINTALOOSA GRULLO
LGR PINTALOOSA GREY
LNB PINTALOOSA BLUE ROAN
LNR PINTALOOSA RED ROAN
LPA PINTALOOSA PALOMINO
LRB PINTALOOSA BAY ROAN
LSR PINTALOOSA SORREL
LSD PINTALOOSA SILVER DAPPLE
LWT PINTALOOSA WHITE
PBA PINTO BAY
PBK PINTO BLACK
PBL PINTO BLUE ROAN
PBR PINTO BROWN
PBS PINTO BUCKSKIN
PCR PINTO CREMELLO
PCS PINTO CHESTNUT
PDN PINTO DUN
PGL PINTO GRULLO
PGR PINTO GREY
PPA PINTO PALOMINO
PRB PINTO ROAN BAY
PRC PINTO ROAN CHESTNUT
PRD PINTO RED DUN
PRG PINTO ROAN GREY
PRK PINTO ROAN BLACK
PRR PINTO ROAN RED
PSD PINTO SILVER DAPPLE
PSR PINTO SORREL
RBA ROAN BAY ROAN
RBK ROAN BLACK ROAN
RBR ROAN BROWN ROAN
RCS ROAN CHESTNUT ROAN
RDN ROAN DUN ROAN
RGR ROAN GREY ROAN
RGN ROAN BLUE ROAN
RNR ROAN RED ROAN
SBA SOLID BAY
SBK SOLID BLACK
SBR SOLID BROWN
SBS SOLID BUCKSKIN
SCR SOLID CREMELLO
SCS SOLID CHESTNUT
SDB SOLID BLUE DUN
SDN SOLID DUN
SDR SOLID RED DUN
SGD SOLID GREY DUN
SGL SOLID GRULLO
SGR SOLID GREY
SPA SOLID PALOMINO
SSR SOLID SORREL
SSD SOLID SILVER DAPPLE
SWT SOLID WHITE
