When using color, it is important that there is a sufficient color contrast between different elements of your design. Higher contrast makes it easier to see, whereas lower contrasts may make it difficult for users to see in high or low light environments. W3C recommends the following contrast ratios:

• 3:1 against the background for large text (14 pt bold, 18pt and up)
• 4.5:1 against the background for small text

Additionally, you should be using visual cues and not just color cues. If you are trying to send an alert whether it is meant to contain an error or not, it is important to have other visual means of conveying a message. This can be done by using words or an icon near the error. Without these other cues, a person who is colorblind may not be able to differentiate between the error field and the fields without errors.