Most casinos use purple for $500 and yellow for $1,000. Beyond that, things are not as standard. It is easy to say that orange and brown are popular, but not everybody follows that convention. Sometimes you see white and blue reemerge. You might say those colors were already used for $1 chips, but the chip sizes get bigger at a certain point, usually at $1,000. The following table shows what I do know.
Chip Colors
Casino$5,000$25,000$100,000 Resorts World Brown Orange Cosmopolitan White Orange Treasure Island White Palazzo/Venetian Brown Orange Grey/brown Green Valley Ranch Brown Circa Orange Wynn White/red Brown Bellagio White Orange Steel blue Golden Nugget Red, white and blue
I would like to thank Mdawg for his help with this question and the pictures.
This question is asked and discussed in my forum at Wizard of Vegas.