When a resource is setup in Web Resource, the resource will have a default target allocation. The target allocation decides the percentage of the user's time that needs to be allocated on various projects. The target is tracked via the 'Allocation Calendar Colors' field on the Allocation Calendar.

When the resource meets the allocation target, then the color changes to Green. Similarly if the resource is understaffed, the color changes to Yellow and if overstaffed, the color changes to Red.The color changes are controlled via the tolerance target set for a resource under their respective profiles. If the actual allocation percentage falls outside the tolerance range (for example, +/- 5%), the task assignments bar on the allocation calendars will, by default, turn red (over-allocated) or yellow (under-allocated).

For example, Resource A is set up with a tolerance range as 5. This implies that if the Resource A is allotted 95% of his time on various projects, then the Allocation Calendar will display a green color for the user. This color will not change unless the allotted time exceeds 100% or falls below 95%. That is the target range acceptable for changing the color on the Allocation Calendar is +/-5%.