## Color Sudoku (Solution)

#### by Byon Garrabrant and Tanya Khovanova

The first eight Sudokus are region Sudokus, where in addition to standard rules you need to satisfy an extra constraint: all letters in one region of color have to be distinct.

Solving Sudokus we get:

#### Blue Solution

```HGD|OTA|WIP
WOI|HDP|TGA
TAP|GWI|DOH
---+---+---
GDO|PAT|IHW
PTW|IHD|OAG
IHA|WOG|PTD
---+---+---
DWG|TIH|APO
APT|DGO|HWI
OIH|APW|GDT
```

#### Green Solution

```FYH|MSN|ILT
MLN|TFI|SHY
TSI|YLH|MFN
---+---+---
NHL|FMT|YSI
YMT|SIL|FNH
SIF|NHY|LTM
---+---+---
HTM|LYS|NIF
IFS|HNM|TYL
LNY|ITF|HMS
```

#### Light Blue Solution

```UCW|NFT|ILE
ENL|UIC|FTW
FTI|EWL|CUN
---+---+---
LIC|TNW|EFU
WET|FCU|LNI
NFU|ILE|TWC
---+---+---
TUN|CEF|WIL
CLF|WUI|NET
IWE|LTN|UCF
```

#### Orange Solution

```HLU|EFP|NSO
SPE|NHO|FUL
FON|SUL|HPE
---+---+---
PEH|LSN|OFU
UNL|FOH|PES
OSF|PEU|LNH
---+---+---
LUS|ONF|EHP
NHO|UPE|SLF
EFP|HLS|UON
```

#### Pink Solution

```TCM|DNR|YFA
ARN|FYM|DTC
DFY|ATC|NMR
---+---+---
NAR|TDF|CYM
YTC|MAN|RDF
FMD|RCY|ANT
---+---+---
MYF|CRD|TAN
CDT|NFA|MRY
RNA|YMT|FCD
```

#### Purple Solution

```OCG|API|MUS
APS|MCU|OGI
UIM|GOS|PCA
---+---+---
MOU|IGA|CSP
IGP|CSM|UAO
CSA|OUP|GIM
---+---+---
GAC|SMO|IPU
SUO|PIC|AMG
PMI|UAG|SOC
```

#### Red Solution

```OEL|CYW|DMA
DAC|ELM|YWO
MWY|DAO|LEC
---+---+---
EOM|LDC|WAY
LYW|OMA|ECD
CDA|YWE|MOL
---+---+---
YCE|WOD|ALM
ALO|MEY|CDW
WMD|ACL|OYE
```

#### Yellow Solution

```YDR|SPU|WEH
PSE|HWD|URY
HWU|ERY|DPS
---+---+---
SPD|RYE|HWU
EYW|UHP|SDR
URH|DSW|PYE
---+---+---
WHY|PUR|ESD
DUP|YES|RHW
RES|WDH|YUP
```

After that we notice that the jigsaw sudoku has the same colors, and the overlap of a particular color is always by three cells. This gives us an idea to use the overlap letters as clues for digits.

We get the following clues for the jigsaw Sudoku.

```  G| NR|I
S|   |D
I |   |  N
---+---+---
GD |   |ESI
|   |
IS |  E|L
---+---+---
L  |  D|A
N  | ES|R
|   |
```

Solving the Jigsaw Sudoku we get

```ELG|SNR|IAD
ANS|EIG|DLR
RIE|LDA|SGN
---+---+---
GDN|RAL|ESI
SAL|IRN|GDE
ISR|DGE|LNA
---+---+---
LEI|NSD|ARG
NGD|AES|RIL
DRA|GLI|NES
```

The colorless white region is the last row and it spells DRAGLINES, which is the answer.