Profile Search does not give exact result for multiple values

the steps
1. Create Custom Data :
Custom Field => Shape (Alphanumeric - Checkbox)
Options => Square, Circular, Triangle
Custom Field => Color (Alphanumeric - Checkbox)
Options => Red, Green, Yellow

2. Create one profile group and add these two custom fields as profile fields

3. Edit to "My Account"
Check options : Shape => Square and Color => Red, Yellow
Save.

4. Now go to Profile Search and try following cases
a. search criteria : color => Red, Yellow
result : gives one contact (correct)
b. search criteria : Shape => Square and color => Red
result : gives one contact (correct)
c. search criteria : Shape => Square and color => Yellow
result : gives one contact (correct)
d. search criteria : Shape => Square and color => Red, Yellow
result : no contact found (wrong.. )