For the prefix, use the day you were born on. For the suffix, use the month. If you're not comfortable sharing your birthday, use a random date— today's date, holiday, etc.

Prefix:
1. Cerulean
2. Indigo
3. Rain
4. Cobalt
5. Pearl
6. Pastel
7. Pale
8. Blue
9. Azure
10. Cold
11. Bright
12. Silver
13. Teal
14. Light
15. Sapphire
16. Mist
17. Fog(gy)
18. Snow
19. Splash
20. Puddle
21. Drizzle
22. Swirl
23. Wet
24. Dew
25. Storm
26. Sky
27. Gray
28. White
29. Cloud
30. Soft
31. Feather

Suffix: stream
January: pelt
February: leaf
March: whisker
April: flower
May: foot
June: belly
July: tail
August: spot
September: blossom
October: step
November: wing
December: feather

I got Pasteltail.

Thanks to thesaurus.com again :3