[Source] Change crosshair color on condition topic

This example works with low ammo but it can of course be customized to work with low health etc..
This only works perfect if you initially had cl_crosshaircolor 5. If you want to use other cl_crosshaircolor's, you'll have to use something else to retrieve the colors (1-4 are hardcoded, easy as fuck).

Code:

---

//get local player
source_engine::CLocalPlayer* pLocalPlayer = (source_engine::CLocalPlayer*)
pClientEntityList->GetClientEntity(pEngineClient->GetLocalPlayerIndex());
if (!pLocalPlayer) return;

//get own weapon
source_engine::CBaseCombatWeapon* pOwnWeapon =
pClientEntityList->GetClientEntityFromHandle<source_engine::CBaseCombatWeapon*>(pLocalPlayer->GetActiveWeapon());
if (!pOwnWeapon) return;

//crosshair coloring
static bool bResetCrosshairColor = false;

std::string const sCmd[4] =
{
        "cl_crosshairalpha",
        "cl_crosshaircolor_r",
        "cl_crosshaircolor_g",
        "cl_crosshaircolor_b"
};

static source_engine::ConVar* pColorCvar[4];
for (int i = 0; i < 4; i++)
        pColorCvar[i] = pCVars->FindVar((char*)sCmd[i].c_str());

static float fCrosshairColorOrg[4];
static float fCrosshairColorSet[4] = { 255.f, 255.f, 0.f, 0.f };
static int iValueToTriggerColorSet = 5;

if (pOwnWeapon->GetAmmoFromClip1() <= iValueToTriggerColorSet)
{
        if (!bResetCrosshairColor)
        {
                for (int i = 0; i < 4; i++)
                        fCrosshairColorOrg[i] = pColorCvar[i]->GetFloat();

                pEngineClient->ClientCmd("cl_crosshaircolor 5");
                char szCommand[256];

                for (int i = 0; i < 4; i++)
                {
                        sprintf_s(szCommand, 256, "%s %f", sCmd[i].c_str(), fCrosshairColorSet[i]);
                        pEngineClient->ClientCmd(szCommand);
                }

                bResetCrosshairColor = true;
        }
}
else
{
        if (bResetCrosshairColor)
        {
                pEngineClient->ClientCmd("cl_crosshaircolor 5");
                char szCommand[256];

                for (int i = 0; i < 4; i++)
                {
                        sprintf_s(szCommand, 256, "%s %f", sCmd[i].c_str(), fCrosshairColorOrg[i]);
                        pEngineClient->ClientCmd(szCommand);
                }

                bResetCrosshairColor = false;
        }
}

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Credits: FrankymanD for the idea

Enjoy.